Electrophotographic photoreceptor and image forming apparatus having the same

ABSTRACT

An object of the invention is to provide a highly reliable electrophotographic photoreceptor having high sensitivity, excellent in light responsivity, not suffering from lowering of such characteristics even when it is used under a low temperature circumstance or in a high speed electrophotographic process, and with less fatigue degradation upon repetitive use. In a photosensitive layer of an electrophotoreceptor, an enamine compound represented by the following general formula (1), for example, the following structural formula is contained as a charge transporting substance, and further at least one of an antioxidant and a light stabilizer is contained. Accordingly, an electrophotographic photoreceptor excellent in sensitivity and light responsivity in various environments, and with less fatigue degradation upon repetitive use is realized.

This application is the US national phase of international applicationPCT/JP2004/007484 filed 31 May 2004 which designated the U.S. and claimspriority to JP 2003-157688 filed 3 Jun. 2003, the entire contents ofeach of which are hereby incorporated by reference.

TECHNICAL FIELD

The present invention concerns an electrophotographic photoreceptor andan image forming apparatus having the same.

BACKGROUND ART

Electrophotographic image forming apparatus (hereinafter also referredto simply as “electrophotographic apparatus”) have been often used, forexample, in copying machines, printers, or facsimile units. In theelectrophotographic apparatus, images are formed by way of the followingelectrophotographic process. At first, the surface of anelectrophotographic photoreceptor provided to the apparatus (hereinafteralso referred to simply as “photoreceptor”) is charged to apredetermined potential uniformly by charging means such as a chargingroller. Exposure is applied to the surface of the charged photoreceptorin accordance with image information to form electrostatic latentimages. The formed electrostatic latent images are developed by adeveloper containing a toner and the like to form toner images asvisible images. The formed toner images are transferred from the surfaceof the photoreceptor to a recording medium such as paper and transferredtoner images are fixed to form images. After the transfer operation, thetoner remaining on the surface of the photoreceptor without beingtransferred is removed by a cleaning blade or the like. Then, thesurface charges on the photoreceptor are eliminated by a light from acharge elimination lamp, by which electrostatic latent images areeliminated from the surface of the photoreceptor.

An electrophotographic photoreceptor comprises a conductive substratemade of a conductive material and a photosensitive layer disposed on theconductive substrate. As the electrophotographic photoreceptor, aninorganic photoreceptor having a photosensitive layer comprising aninorganic photoconductive material such as selenium, zinc oxide orcadmium as a main ingredient has been used generally. While theinorganic photoreceptor has basic properties as the photoreceptor tosome extent, it involves a problem that the formation of the film forthe light sensitive layer is difficult, plasticity is poor, and theproduction cost is expensive. Further, the inorganic photoconductivematerial generally has high toxicity and suffers from great restrictionin view of production and handling.

On the other hand, since an organic photoreceptor using an organicphotoconductive material has advantages that it has good film formingproperty for a photosensitive layer, excellent flexibility, reducedweight and good transparency and a photoreceptor showing favorablesensitivity to wavelength region over a wide range can be easilydesigned by an appropriate sensitizing method, it has been graduallydeveloped as a main material for the electrophotographic photoreceptor.While the organic photoreceptor in the initial state has drawback inview of the sensitivity and the durability, such drawbacks have beenimproved remarkably by the development of a function separatedelectrophotographic photoreceptor in which a charge generation functionand a charge transportation function are shared to separate materialsrespectively.

The function separated photoreceptor includes a layered type and asingle layer type. In the layered type photoreceptor, for example, aphotoconductive layer in which a charge generating layer containing acharge generating substance sharing a charge generation function and acharge transporting layer containing a charge transporting substancesharing a charge transportation function are laminated is provided as aphotosensitive layer. In the single layer type function separatedphotoreceptor, a single photoconductive layer containing both a chargegenerating substance and a charge transporting substance is disposed asa photosensitive layer. The function separated photoreceptor describedabove also has an advantage that a selection range for the chargegenerating substance and the charge transporting substance constitutingthe light sensitive layer is wide and a photoreceptor having optionalcharacteristics can be manufactured relatively easily.

As the charge generating substance used in the function separatedphotoreceptor, various substances such as phthalocyanine pigment,squarylium dye, azo pigment, perylene pigment, polynuclear quinonepigment, cyanine dye, squaric acid dye, and pyrylium salt dye have beenstudied and various materials of excellent light fastness and havinghigh charge generating ability have been proposed.

On the other hand, various compounds are known for the chargetransporting substances, including, for example, pyrazoline compounds(e.g., refer to Japanese Examined Patent Publication JP-B2 52-4188(1977)), hydrazone compounds (e.g., refer to Japanese Unexamined PatentPublication JP-A 54-150128 (1979), Japanese Examined Patent PublicationJP-B2 55-42380 (1980), and Japanese Unexamined Patent Publication JP-A55-52063 (1980)), triphenylamine compounds (e.g., refer to JapaneseExamined Patent Publication JP-B2 58-32372 (1983) and JapaneseUnexamined Patent Publication JP-A 2-190862 (1990)) and stilbenecompounds (e.g., refer to Japanese Unexamined Patent Publications JP-A54-151955 (1979) and JP-A 58-198043 (1983)). Recently, pyrenederivatives, naphthalene derivatives and terphenyl derivatives that havea condensed polycyclic hydrocarbon structure as the center nucleus havebeen developed (e.g., refer to Japanese Unexamined Patent PublicationJP-A 7-48324 (1995)).

The charge transporting substances must satisfy the followingrequirements:

-   (1) they are stable to light and heat;-   (2) they are stable to active substances such as ozone, nitrogen    oxides (NOx) and nitric acid that may be generated in corona    discharging on a photoreceptor;-   (3) they have good charge transportability;-   (4) they are compatible with organic solvents and binder resins;-   (5) they are easy to produce and are inexpensive. Though partly    satisfying some of these, however, the charge transporting    substances disclosed in the above-mentioned patent publications    could not satisfy all of these at high level.

Further, the charge transporting substance is required to have highlycharge transportability, particularly, among the requirements describedabove. For example, in a case where the charge transporting layer inwhich a charge transporting substance is dispersed in the binder resinforms the surface layer of the photoreceptor, particularly high chargetransportability is required for the charge transporting substance inorder to ensure a sufficient light sensitivity.

In a case where, the photoreceptor is used being mounted on anelectrophotographic apparatus, such as a copying machine or a laser beamprinter, the surface layer of the photoreceptor is inevitably scrapedoff partially by a contact member such as a cleaning blade or a chargingroller. In a case where the surface layer of the photoreceptor isscraped, the charge retainability of the photoreceptor lowers and imagesof good quality can no more be provided. Accordingly, for improving thedurability of the copying machine, the laser beam printer, etc. it hasbeen demanded for a photoreceptor having a surface layer resistant tothe contact member, that is, a surface layer of high printing resistancewith less amount scraped by the contact member.

In order to improve the durability of the photoreceptor by increasingthe printing resistance of the surface layer, it may be considered toincrease the content of the binder resin in the charge transportinglayer as the surface layer. However, as the content of the binder resinin the charge transporting layer increases, it results in a problem thatthe light responsivity lowers. In a case where the light responsivity islow, that is, the decay speed of the surface potential after exposure isslow, since it is used repetitively in a state where the residualpotential increases and the surface potential of the photoreceptor isnot sufficiently decayed, the surface charges at the portion to beerased by the exposure are not erased sufficiently to result in troublessuch as early lowering of the image quality.

Lowering of the light responsivity is attributable to a low chargetransportability of the charge transporting substance. In the functionseparated photoreceptor, surface charges on the photoreceptor irradiatedwith a light are eliminated when charges generated in the chargegenerating substance by light absorption are transported by the chargetransporting substance to the surface of the photoreceptor. Therefore,in a care where the content of the charge transporting substance in thecharge transporting layer is lowered relatively along with increase ofthe content of the binder resin, the charge transportability of thecharge transporting layer is further lowered when the chargetransportability of the charge transporting substance is low to lowerthe light responsivity as described above. Accordingly, in order toprevent lowering of the light responsivity and ensure a sufficient lightresponsivity, a high charge transportability is required for the chargetransporting substance.

Further, the size has been reduced and the speed has been increasedrecently in electrophotographic apparatus, for example, digital copyingmachines and printers, and improvement for the sensitivity has beenrequired as the characteristics of the photoreceptor for coping with theincrease of the speed, and high charge transportability has beendemanded more and more as the charge transporting substance. Further, inthe high speed electrophotographic process, since the time from exposureto development is short, a photoreceptor of high light responsivity isdemanded. As described above, since the light responsivity depends onthe charge transportability of the charge transporting substance, acharge transporting substance having a higher charge transportability isdemanded also with such a view point.

As the charge transporting substance capable of satisfying such ademand, an enamine compound having a charge movability higher than thatof the charge transporting substance described above has been proposed(refer, for example, to Japanese Unexamined Patent Publications JP-A2-51162 (1990), JP-A 6-43674 (1994) and JP-A 10-69107 (1998)).

Further, a photoreceptor provided with a high charge transportability bythe incorporation of a polysilane and improved with the chargeabilityand the film strength by the incorporation of an enamine compound havinga specific structure has been proposed (refer to Japanese UnexaminedPatent Publication JP-A 7-134430 (1995)).

On the other hand, in the electrophotographic process, the photoreceptoris exposed to an active gas such as ozone or NOx generated duringcharging by corona discharge, UV-rays contained in a light used forexposure and charge elimination, or heat. In a case where thephotoreceptor is exposed to the active gas, UV-rays, or heat describedabove, free radicals are generated in the photosensitive layer todecompose or degrade the materials constituting the photosensitivelayer. Accordingly, the charge transporting substance is required to bestable against light, heat, and active gas such as ozone or NOx asdescribed above. However, charge transporting substance capable ofsatisfying such requirements has not yet been obtained and in a casewhere the photoreceptor is used repetitively, fatigue degradation suchas lowering of the charge potential, increase of the residual potential,and lowering of the sensitivity are caused, particularly, due to thedecomposition or degradation of the material consisting thephotosensitive layer, particularly, the charge transporting substance toresult in a problem of degradation of the image quality.

As the technique for preventing decomposition and degradation and formitigating the fatigue degradation upon repetitive use of the chargetransporting substance, etc. it has been known to add an antioxidant ora light stabilizer to the photosensitive layer (for example, refer toJapanese Examined Patent Publication JP-B2 2730744). However, when theantioxidant or light stabilizer is added to the photosensitive layer,while the fatigue degradation can be mitigated, it results in a problemof lowering the sensitivity and the light responsivity. Lowering of thesensitivity and the light responsivity develops particularly remarkablyunder a low temperature circumstance.

In order to suppress the lowering of the sensitivity and the lightresponsivity upon addition of the antioxidant, light stabilizer, etc. itmay be considered to use a charge transporting substance of high chargemovability. Then, it has been studied on combined use of the antioxidantand the light stabilizer with a specified charge transporting substance.For example, it has been proposed a combination of a hydrazone compoundand an antioxidant (refer to Japanese Unexamined Patent Publication JP-A64-44946 (1989)), a combination of an alkenylamine compound and anantioxidant (refer to Japanese Unexamined Patent Publication JP-A11-271995 (1999)), and a combination of a diamine compound and a lightstabilizer (refer to Japanese Unexamined Patent Publication JP-A2001-51434).

Also in a case of using the antioxidant and the light stabilizer incombination with the specified charge transporting substance asdescribed in JP-A 64-44946, 11-271995, and 2001-51434, its involves aproblem that degradation due to repetitive use can not be improvedsufficiently for those having good initial sensitivity, while theinitial sensitivity and the chargeability are not sufficient for thoseshowing a less degradation by the repetitive use.

Further, no sufficient sensitivity and light responsivity can beobtained under a low temperature circumstance even by the combined useof the antioxidant and the light stabilizer with the enamine compound ofhigh charge transportability as described in JP-A 2-51162, 6-43674 or10-69107. Further, in the photoreceptor described in JP-A 7-134430,while a high charge transportability is provided by the incorporation ofpolysilane, the photoreceptor using polysilane involves a problem thatit is sensitive to light exposure and characteristic as thephotoreceptor is lowered by exposure to light, for example, duringmaintenance even when the light stabilizer is added to thephotosensitive layer.

DISCLOSURE OF THE INVENTION

It is an object of the invention to provide a highly reliableelectrophotographic photoreceptor having high sensitivity, excellent inlight responsivity, not suffering from lowering of such characteristicseven when it is used under a low temperature circumstance or in a highspeed electrophotographic process, or when it is exposed to light andstable against an active gas such as ozone or NOx, UV-rays, and heat,and with less fatigue degradation upon repetitive use, as well as animage forming apparatus having the same.

The invention provides an electrophotographic photoreceptor comprising:

a conductive substrate composed of a conductive material; and

a photosensitive layer disposed on the conductive substrate andcontaining an enamine compound represented by the following generalformula (1), and at least one of an antioxidant and a light stabilizer.

wherein Ar¹ and Ar² each represent an aryl group which may have asubstituent or a heterocyclic group which may have a substituent; Ar³represents an aryl group which may have a substituent, a heterocyclicgroup which may have a substituent, an aralkyl group which may have asubstituent, or an alkyl group which may have a substituent; Ar⁴ and Ar⁵each represent a hydrogen atom, an aryl group which may have asubstituent, a heterocyclic group which may have a substituent, anaralkyl group which may have a substituent, or an alkyl group which mayhave a substituent, but it is excluded that Ar⁴ and Ar⁵ are hydrogenatoms at the same time; Ar⁴ and Ar⁵ may bond to each other via an atomor an atomic group to form a cyclic structure; “a” represents an alkylgroup which may have a substituent, an alkoxy group which may have asubstituent, a dialkylamino group which may have a substituent, an arylgroup which may have a substituent, a halogen atom, or a hydrogen atom;m indicates an integer of from 1 to 6; when m is 2 or more, then the“a”s may be the same or different and may bond to each other to form acyclic structure; R¹ represents a hydrogen atom, a halogen atom, or analkyl group which may have a substituent; R², R³ and R⁴ each represent ahydrogen atom, an alkyl group which may have a substituent, an arylgroup which may have a substituent, a heterocyclic group which may havea substituent, or an aralkyl group which may have a substituent; nindicates an integer of from 0 to 3; when n is 2 or 3, then the R²s maybe the same or different and the R³s may be the same or different, butwhen n is 0, Ar³ is a heterocyclic group which may have a substituent.

In accordance with the invention, the electrophotographic photoreceptorhas a conductive substrate and a photosensitive layer and thephotosensitive layer contains an enamine compound represented by thegeneral formula (1) and at least one of an antioxidant and a lightstabilizer. The photosensitive layer may be any one of a photosensitivelayer constituted with a single photoconductive layer containing acharge generating substance and a charge transporting substance, aphotosensitive layer constituted with a photoconductive layer in which acharge generating layer containing a charge generating substance and acharge transporting layer containing a charge transporting substance arestacked, and a photosensitive layer in which a surface protective layeris further stacked on the photoconductive layer described above. Sincethe enamine compound represented by the general formula (1) has a highcharge movability, by incorporating the enamine compound represented bythe general formula (1) as the charge transporting substance in thephotosensitive layer, it is possible to obtain an electrophotographicphotoreceptor having high chargeability, sensitivity and lightresponsivity, and not suffering from lowering of such characteristicseven when it is used under a low temperature circumstance or in a highspeed electrophotographic process. Further, since a high chargetransportability can be attained without incorporating polysilane in thephotosensitive layer, the characteristics described above are notlowered even when the electrophotographic photoreceptor is exposed tolight.

Further, since at least one of the antioxidant and the light stabilizeris incorporated in the photosensitive layer, the fatigue degradationupon repetitive use can be mitigated to improve the durability of theelectrophotographic photoreceptor. This is considered to be attributableto that the antioxidant and the light stabilizer contained in thephotosensitive layer react preferentially with free radicals generatedin the photosensitive layer by an active gas such as ozone or NOxgenerated during charging by the corona discharge, as well as UV-raysand heat contained in light used for exposure and charge elimination,thereby preventing decomposition or degradation of the enamine compoundrepresented by the general formula (1) contained as the chargetransporting substance. In a case where at least one of the antioxidantand the light stabilizer is incorporated in the photosensitive layer,since at least one of the antioxidant and the light stabilizer isincorporated in the coating solution upon forming the photosensitivelayer by coating, the stability of the coating solution can be improved.Accordingly, since an electrophotographic photoreceptor havingsubstantially identical characteristics can be manufactured in a case offorming a photosensitive layer soon after the preparation of a coatingsolution or in a case of forming a photosensitive layer after lapse of along time, it is possible to improve the stability for quality and theproductivity of an electrophotographic photoreceptor.

In the electrophotographic photoreceptor according to the invention,since the enamine compound of high charge movability represented by thegeneral formula (1) is contained as the charge transporting substance inthe photosensitive layer, the sensitivity and the light responsivity arenot lowered through the antioxidant and the light stabilizer areincorporated in the photosensitive layer.

Accordingly, by incorporating the enamine compound represented by thegeneral formula (1) and at least one of the antioxidant and the lightstability in combination into the photosensitive layer as describedabove, it is possible to obtain a highly reliable electrophotographicphotoreceptor having high chargeability, sensitivity, and lightresponsivity, not suffering from lowering of the characteristicsdescribed above even when it is used under a low temperaturecircumstance or in a high speed electrophotographic process, or when itis exposed to light, stable against the active gas such as ozone or NOx,UV-rays and heat, and with less fatigue degradation upon repetitive use.

Further, the invention is characterized in that the enamine compoundrepresented by the general formula (1) is an enamine compoundrepresented by the following general formula (2).

wherein “b”, “c” and “d” each represent an alkyl group which may have asubstituent, an alkoxy group which may have a substituent, adialkylamino group which may have a substituentv, an aryl group whichmay have a substituent, a halogen atom, or a hydrogen atom; “i”, “k” and“j” each indicate an integer of from 1 to 5; when “i” is 2 or more, thenthe “b”s may be the same or different and may bond to each other to forma cyclic structure; when “k” is 2 or more, then the “c”s may be the sameor different and may bond to each other to form a cyclic structure; andwhen “j” is 2 or more, then the “d”s may be the same or different andmay bond to each other to form a cyclic structure; Ar⁴, Ar⁵, “a” and “m”represent the same as those defined in formula (1).

In accordance with the invention, since the enamine compound representedby the general formula (2) having particularly high charge movabilityamong the enamine compounds represented by the general formula (1) iscontained in the photosensitive layer, it is possible to obtain anelectrophotographic photoreceptor having higher sensitivity and lightresponsivity. Further, since the enamine compound represented by thegeneral formula (2) can be synthesized relatively easily and shows highyield among the enamine compounds represented by the general formula(1), it can be manufactured at a reduced cost. Accordingly, theelectrophotographic photoreceptor of the invention having the excellentcharacteristics as described above can be manufactured at a reducedmanufacturing cost.

Further, the invention is characterized in that the enamine compoundrepresented by the general formula (1) is an enamine compoundrepresented by the following general formula (1a).

wherein Ar¹ and Ar² each represents a phenyl group; Ar³ represents atolyl group, p-methoxyphenyl group, naphthyl group, or5-methyl-2-thienyl group; Ar⁴ represents a hydrogen atom, lower alkylgroup or phenyl group; Ar⁵ represents a phenyl group or p-methoxyphenylgroup; and n represents an integer of 1 to 2.

The compound of the general formula (1a) not only has high chargemovability but also can be manufactured at a reduced cost since thesynthesis is easy and the yield is high. Accordingly, theelectrophotographic photoreceptor containing the compound of theinvention has high sensitivity, and is excellent in the responsivity andalso excellent in view of the cost.

Further, the invention is characterized in that the antioxidant is ahindered phenol compound having a hindered phenol structural unit.

Further, the invention is characterized in that the hindered phenolcompound is a compound represented by the following structural formula(I-a).

In accordance with the invention, the photosensitive layer contains, asan antioxidant, a hindered phenol compound having a hindered phenolstructural unit, preferably, a hindered phenol compound represented bythe structural formula (I-a). By the incorporation of the hinderedphenol compound, particularly, the hindered phenol compound representedby the structural formula (I-a) in the photosensitive layer,decomposition or degradation of the enamine compound represented by thegeneral formula (1) contained as the charge transporting substance inthe photosensitive layer can be suppressed particularly to furthermitigate the fatigue degradation upon repetitive use and the durabilityof the electrophotographic photoreceptor can be improved further.Further, the stability of the coating solution upon forming thephotosensitive layer by coating can be improved further to furtherimprove the stability for the quality and the productivity of theelectrophotographic photoreceptor.

Further, the invention is characterized in that the antioxidant is aphosphoric antioxidant.

In accordance with the invention, the photosensitive layer contains thephosphoric antioxidant. By the incorporation of the phosphoricantioxidant in the photosensitive layer, decomposition or degradation ofthe enamine compound represented by the general formula (1) contained asthe charge transporting substance in the photosensitive layer can besuppressed particularly to further mitigate the fatigue degradation uponrepetitive use and further improve the durability of theelectrophotographic photoreceptor. Further, the stability of the coatingsolution upon forming the photosensitive layer by coating can beimproved further to further improve the stability for quality and theproductivity of the electrophotographic photoreceptor.

Further the invention is characterized in that the antioxidant is anorganic sulfuric antioxidant.

In accordance with the invention, the photosensitive layer contains theorganic sulfuric antioxidant. By the incorporation of the organicsulfuric antioxidant in the photosensitive layer, decomposition ordegradation of the enamine compound represented by the general formula(1) contained as the charge transporting substance in the photosensitivelayer can be suppressed particularly to further mitigate the fatiguedegradation upon repetitive use and further improve the durability ofthe electrophotographic photoreceptor. Further, the stability of thecoating solution upon forming the photosensitive layer by coating can beimproved further to further improve the stability of quality and theproductivity of the electrophotographic photoreceptor.

Further, the invention is characterized in that the light stabilizer isa hindered amine compound having a hindered amine structural unit.

Further, the invention is characterized in that the hindered aminecompound is a compound represented by the following structural formula(II-a).

In accordance with the invention, the photosensitive layer contains, asa light stabilizer, a hindered amine compound having a hindered aminestructural unit, preferably, a hindered amine compound represented bythe structural formula (II-a). Decomposition or degradation of theenamine compound represented by the general formula (1) contained as thecharge transporting substance in the photosensitive layer is suppressedparticularly to further mitigate the fatigue degradation upon repetitiveuse and further improve the durability of the electrophotographicphotoreceptor. Further, the stability of the coating solution uponforming the photosensitive layer by coating can be improved further tofurther improve the stability of quality and the productivity of theelectrophotographic photoreceptor.

Further, the invention is characterized in that the light stabilizer isa benzotriazole derivative.

In accordance with the invention, the photosensitive layer contains abenzotriazole derivative as a light stabilizer. By the incorporation ofthe benzotriazole derivative in the photosensitive layer, decompositionor degradation of the enamine compound represented by the generalformula (1) contained as the charge transporting substance in thephotosensitive layer is suppressed particularly to further mitigate thefatigue degradation upon repetitive use and further improve thedurability of the electrophotographic photoreceptor. Further, thestability of the coating solution upon forming the photosensitive layerby coating can be further improved to further improve the stability ofquality and the productivity of the electrophotographic photoreceptor.

Further, the invention is characterized in that the photosensitive layercontains 0.1 to 15% by weight of the antioxidant.

In accordance with the invention, since the content of the antioxidantcontained in the photosensitive layer is selected to a suitable range,an effect sufficient to the improvement of the durability of theelectrophotographic photoreceptor and the improvement of the stabilityof the coating solution can be obtained, and lowering of thecharacteristics of the electrophotographic photoreceptor by theincorporation of the antioxidant can be minimized.

Further, the invention is characterized in that the photosensitive layercontains 0.1 to 10% by weight of the light stabilizer.

In accordance with the invention, since the content of the lightstabilizer contained in the photosensitive layer is selected to asuitable range, an effect sufficient to the improvement of thedurability of the electrophotographic photoreceptor and the improvementof the stability of the coating solution can be obtained, and loweringof the characteristics of the electrophotographic photoreceptor by theincorporation of the light stabilizer can be minimized.

Further, the invention provides an image forming apparatus comprising:

the electrophotographic photoreceptor of the invention;

charging means for charging the electrophotographic photoreceptor;

exposure means for applying exposure to the charged electrophotographicphotoreceptor; and

developing means for developing electrostatic latent images formed byexposure.

In accordance with the invention, the image forming apparatus has theelectrophotographic photoreceptor of the invention, the charging means,the exposure means and the developing means. The electrophotographicphotoreceptor of the invention has high chargeability, sensitivity andlight responsivity, does not suffer from lowering of the characteristicsdescribed above even in a case when it is used under a low temperaturecircumstance or in a high speed electrophotographic process, is stableagainst an active gas such as ozone or NOx, UV-rays and heat, suffersfrom less fatigue degradation upon repetitive use and has highreliability. Accordingly, a highly reliable image forming apparatuscapable of providing high quality image stably for a long time undervarious circumstances can be obtained. Further, since theelectrophotographic photoreceptor of the invention does not suffer fromlowering of the characteristics described above even in a case when itis exposed to light, it is possible to prevent lowering of image qualitycaused by exposure of the electrophotographic photoreceptor to lightduring maintenance or the like to improve the reliability of the imageforming apparatus.

BRIEF DESCRIPTION OF DRAWINGS

Other and further objects, features, and advantages of the inventionwill be more explicit from the following detailed description taken withreference to the drawings wherein:

FIG. 1A is a perspective view schematically showing the constitution ofan electrophotographic photoreceptor 1 according to a first embodimentof the invention, and FIG. 1B is a fragmentary cross sectional viewschematically showing the constitution of the electrophotographicphotoreceptor 1;

FIG. 2 is a cross sectional view schematically showing the constitutionof an electrophotographic photoreceptor according to a second embodimentof the invention;

FIG. 3 is a cross sectional view schematically showing the constitutionof an electrophotographic photoreceptor according to a third embodimentof the invention;

FIG. 4 is a side elevational view for an arrangement schematicallyshowing the constitution of an image forming apparatus 100;

FIG. 5 is a ¹H-NMR spectrum of a product in Production Example 1-3;

FIG. 6 is an enlarged view of the spectrum of FIG. 5 in the range offrom 6 ppm to 9 ppm;

FIG. 7 is a ¹³C-NMR spectrum in ordinary measurement of the product inProduction Example 1-3;

FIG. 8 is an enlarged view of the spectrum of FIG. 7 in the range offrom 110 ppm to 160 ppm;

FIG. 9 is a ¹³C-NMR spectrum in DEPT135 measurement of the product inProduction Example 1-3;

FIG. 10 is an enlarged view of the spectrum of FIG. 9 in the range offrom 110 ppm to 160 ppm;

FIG. 11 is a ¹H-NMR spectrum of the product in Production Example 2;

FIG. 12 is an enlarged view of the spectrum of FIG. 11 in the range offrom 6 ppm to 9 ppm;

FIG. 13 is a ¹³C-NMR spectrum in ordinary measurement of the product inProduction Example 2;

FIG. 14 is an enlarged view of the spectrum of FIG. 13 in the range offrom 110 ppm to 160 ppm;

FIG. 15 is a ¹³C-NMR spectrum in DEPT135 measurement of the product inProduction Example 2; and

FIG. 16 is an enlarged view of the spectrum of FIG. 15 in the range offrom 110 ppm to 160 ppm.

BEST MODE FOR CARRYING OUT THE INVENTION

Now referring to the drawings, preferred embodiments of the inventionare described below. However, the invention is not restricted to theembodiments.

FIG. 1A is a perspective view schematically showing the constitution ofan electrophotographic photoreceptor 1 according to a first embodimentof the invention. FIG. 1B is a fragmentary cross sectional viewschematically showing the constitution of the electrophotographicphotoreceptor 1. The electrophotographic photoreceptor 1 (hereinafteralso referred to simply as “photoreceptor”) includes a cylindricalconductive substrate 11 composed of a conductive material, and aphotosensitive layer 14 disposed on the circumferential surface of theconductive substrate 11. The photosensitive layer 14 is constituted witha photoconductive layer in which a charge generating layer 15 containinga charge generating substance 12 that generates charges by absorption oflight and a charge transporting layer 16 containing a chargetransporting substance 13 having a function of receiving chargesgenerated by the charge generating substance 12 and transporting themare stacked in this order on an outer circumferential surface of theconductive substrate 11. That is, the electrophotographic photoreceptor1 is a layered photoreceptor.

The photosensitive layer 14 contains at least one of an antioxidant anda light stabilizer. The antioxidant and the light stabilizer may becontained in either of the charge generating layer 15 and the chargetransporting layer 16 constituting the photosensitive layer 14, or maybe contained in both of the charge generating layer 15 and the chargetransporting layer 16. It is preferred that the antioxidant and thelight stabilizer are contained at least in the charge transporting layer16.

For the charge transporting substance 13 contained in the chargetransporting layer 16, an enamine compound represented by the followingformula (1) is used.

In the general formula (1), Ar¹ and Ar² each represent an aryl groupwhich may have a substituent or a heterocyclic group which may have asubstituent; Ar³ represents an aryl group which may have a substituent,a heterocyclic group which may have a substituent, an aralkyl groupwhich may have a substituent, or an alkyl group which may have asubstituent; Ar⁴ and Ar⁵ each represent a hydrogen atom, an aryl groupwhich may have a substituent, a heterocyclic group which may have asubstituent, an aralkyl group which may have a substituent, or an alkylgroup which may have a substituent, but it is excluded that Ar⁴ and Ar⁵are hydrogen atoms at the same time; Ar⁴ and Ar⁵ may bond to each othervia an atom or an atomic group to form a cyclic structure; “a”represents an alkyl group which may have a substituent, an alkoxy groupwhich may have a substituent, a dialkylamino group which may have asubstituent, an aryl group which may have a substituent, a halogen atom,or a hydrogen atom; m indicates an integer of from 1 to 6; when m is 2or more, then the “a”s may be the same or different and may bond to eachother to form a cyclic structure; R¹ represents a hydrogen atom, ahalogen atom, or an alkyl group which may have a substituent; R², R³ andR⁴ each represent a hydrogen atom, an alkyl group which may have asubstituent, an aryl group which may have a substituent, a heterocyclicgroup which may have a substituent, or an aralkyl group which may have asubstituent; n indicates an integer of from 0 to 3; when n is 2 or 3,then the R²s may be the same or different and the R³s may be the same ordifferent, but when n is 0, Ar³ is a heterocyclic group which may have asubstituent.

In the general formula (1), specific examples of the aryl grouprepresented by Ar¹, Ar², Ar³, Ar⁴, Ar⁵, “a”, R², R³ or R⁴ can include,for example, phenyl, naphthyl, pyrenyl and anthonyl. A substituent whichmay be present on the aryl group include, for example, alkyl groups suchas methyl, ethyl, propyl and trifluoromethyl, alkenyl groups such as2-propenyl and styryl, alkoxy groups such as methoxy, ethoxy andpropoxy, amino groups such as methylamino and dimethylamino, halogenogroups such as fluoro, chloro and bromo, aryl groups such as phenyl andnaphthyl, aryloxy groups such as phenoxy, and arylthio groups such asthiophenoxy. Specific examples of the aryl group having suchsubstituents can include tolyl, methoxyphenyl, biphenylyl, terphenyl,phenoxyphenyl, p-(phenylthio)phenyl and p-styrylphenyl.

In the general formula (1), specific examples of the heterocyclic grouprepresented by Ar¹, Ar², Ar³, Ar⁴, Ar⁵, R², R³ or R⁴ can include furyl,thienyl, thiazoryl, benzofuryl, benzothiophenyl, benzothiazoryl andbenzooxazoryl. A substituent which may be present on the heterocyclicgroup described above can include, for example, substituents similar tothose which may be present on the aryl group represented by Ar¹ and thelike described above, and specific examples of the heterocyclic grouphaving a substituent can include N-methyl indolyl and N-ethylcarbazolyl.

In the general formula (1), specific examples of the aralkyl group ofAr³, Ar⁴, Ar⁵, R², R³ or R⁴ can include, for example, benzyl and1-naphthylmethyl. A substituent which may be present on the aralkylgroup described above can include, for example, substituents similar tothose which may be present on the aryl group represented by Ar¹ and thelike described above, and specific examples of the aralkyl group havinga substituent can include p-methoxybenzyl.

In the general formula (1), as the alkyl group represented by Ar³, Ar⁴,Ar⁵, “a”, R¹, R², R³ or R⁴, those having from 1 to 6 carbon atoms arepreferred, and specific examples thereof can include chained alkylgroups such as methyl, ethyl, n-propyl, isopropyl and t-butyl, andcycloalkyl groups such as cyclohexyl and cyclopentyl. A substituentwhich may be present on the alkyl groups described above can includesubstituents similar to those which may be present on the aryl grouprepresented by Ar¹ described above, and specific examples of the alkylgroup having a substituent can include halogenated alkyl groups such astrifluoromethyl and fluoromethyl, alkoxyalkyl groups such as1-methoxyethyl, and alkyl groups substituted with a heterocyclic groupsuch as 2-thienylmethyl.

In the general formula (1), as the alkoxy group represented by “a”,those having from 1 to 4 carbon atoms are preferred, and specificexamples can include methoxy, ethoxy, n-propoxy and isopropoxy. Asubstituent which may be present on the alkyl group described above caninclude substituents similar to those which may be present on the arylgroup represented by Ar¹ described above.

In the general formula (1), as the dialkylamino group represented by“a”, those having from 1 to 4 carbon atoms substituted with an alkylgroup are preferred, and specific examples can include, dimethylamino,diethylamino and diisopropylamino. A substituent which may be present onthe dialylamino group can include, for example, substituents similar tothose which may be present on the aryl group represented by Ar¹.

In the general formula (1), specific examples of the halogen atomrepresented by “a” or R¹ can include a fluorine atom and a chlorineatom.

In the general formula (1), specific examples of the atoms for bondingAr⁴ and Ar⁵ can include an oxygen atom, sulfur atom and nitrogen atom.The nitrogen atom, for example, as a bivalent group such as an iminogroup or N-alkylimino group, bonds Ar⁴ and Ar⁵. Specific examples of theatomic group for bonding Ar⁴ and Ar⁵ can include bivalent groups, forexample, an alkylene group such as methylene, ethylene andmethylmethylene, an alkenylene group such as vinylene and propenylene,an alkylene group containing a hetero atom such as oxymethylene(chemical formula: —O—CH₂—), and an alkenylene group containing a heteroatom such as thiovinylene (chemical formula: S—CH═CH—).

Since the enamine compound represented by the general formula (1) has ahigh charge movability, by the incorporation of the enamine compoundrepresented by the general formula (1) as the charge transportingsubstance 13 in the photosensitive layer 14, it is possible to obtain anelectrophotographic photoreceptor 1 having high chargeability,sensitivity and light responsivity and not suffering from lowering ofthe characteristics described above even in a case where it is usedunder a low temperature circumstance or in a high speedelectrophotographic process. Further, since high charge movability canbe attained without incorporating polysilane in the photosensitive layer14, the characteristics described above are not lowered even in a casewhere the electrophotographic photoreceptor 1 is exposed to a light.

Further, since at least one of the antioxidant and the light stabilizeris contained in the photosensitive layer 14 as described above, fatiguedegradation upon repetitive use can be mitigated to improve thedurability of the electrophotographic photoreceptor 1. This isconsidered to be attributable to that the antioxidant and the lightstabilizer contained in the photosensitive layer 14 react preferentiallywith free radicals generated in the photosensitive layer 14 by an activegas such as ozone or NOx generated during charging by the coronadischarge, as well as UV-rays and heat contained in light used forexposure and charge elimination, thereby preventing decomposition ordegradation of the enamine compound represented by the general formula(1) contained as the charge transporting substance 13. Further, in acase where at least one of the antioxidant and the light stabilizer iscontained in the photosensitive layer 14, since at least one of theantioxidant and the light stabilizer is contained in the coatingsolution upon forming the photosensitive layer 14 by coating, thestability of the coating solution can be improved. Accordingly, even ina case of forming the photosensitive layer 14 just after preparation ofthe coating solution or in a case of forming the photosensitive layer 14after lapse of long time, since an electrophotographic photoreceptor 1having substantially identical characteristics can be manufactured, thestability of quality and the productivity of the electrophotographicphotoreceptor 1 can be improved.

In a case of incorporating the antioxidant and the light stabilizer inthe photosensitive layer 14, while the sensitivity and the lightresponsivity may be lowered sometimes, since the electrophotographicphotoreceptor 1 of this embodiment contains the enamine compound of highcharge movability represented by the general formula (1) as the chargetransporting substance 13 in the photosensitive layer 14 as describedabove, the sensitivity and the light responsivity are not lowered evenwhen the antioxidant and the light stabilizer is contained in thephotosensitive layer 14.

Accordingly, by the incorporation of the enamine compound represented bythe general formula (1) and at least one of antioxidant and the lightstabilizer in combination in the light sensitive layer 14 as describedabove, it is possible to obtain highly reliable electrophotographicphotoreceptor 1 having high chargeability, sensitivity and lightresponsivity, not suffering from lowering of the characteristics even ina case where it is used under a low temperature circumstance or in ahigh speed photographic process or when it is exposed to light, stableagainst an active gas such as ozone or NOx, UV-rays and heat, and withless fatigue deterioration upon repetitive use.

For the charge transporting substance 13, an enamine compoundrepresented by the following general formula (2), among enaminecompounds represented by the general formula (1), is preferably used.

In the general formula (2), “b”, “c” and “d” each represent an alkylgroup which may have a substituent, an alkoxy group which may have asubstituent, a dialkylamino group which may have a substituent, an arylgroup which may have a substituent, a halogen atom, or a hydrogen atom;“i”, “k” and “j” each indicate an integer of from 1 to 5; when “i” is 2or more, then the “b”s may be the same or different and may bond to eachother to form a cyclic structure; when “k” is 2 or more, then the “c”smay be the same or different and may bond to each other to form a cyclicstructure; and when “j” is 2 or more, then the “d”s may be the same ordifferent and may bond to each other to form a cyclic structure; Ar⁴,Ar⁵, “a” and “m” represent the same as those defined in formula (1).

In the general formula (2), the alkyl group represented by b, c or d ispreferably those having from 1 to 6 carbon atoms, and specific examplesthereof can include chained alkyl groups such as methyl, ethyl, n-propyland isopropyl, and cycloalkyl groups such as cyclohexyl and cyclopentyl.A substituent which may be present on the alkyl group described abovecan include, for example, substituents similar to those which may bepresent on the aryl group represented by Ar¹ and the like describedabove, and the specific examples of the alkyl group having a substituentcan include halogenated alkyl groups such as trifluoromethyl andfluoromethyl and alkoxyalkyl groups such as 1-methylethyl and alkylgroups substituted with a heterocyclic group such as 2-thienylmethyl.

In the general formula (2), the alkoxy group represented by b, c or d ispreferably those having from 1 to 4 carbon atoms, and specific examplesthereof can include, methoxy, ethoxy, n-propoxy and isopropoxy. Asubstituent which may be present on the alkyl groups can have caninclude, for example, substituents similar to those which may be presenton the aryl group represented by Ar¹ and the like described above.

In the general formula (2), the dialkyl group represented by b, c or dis preferably those substituted with an alkyl group having from 1 to 4carbon atoms, and specific examples thereof can include dimethylamino,diethylamino and diisopropylamino. A substituent which the dialkylaminogroups can include, for example, substituents similar to those which maybe present on the aryl group represented by Ar¹ and the like describedabove.

In the general formula (2), specific examples of the aryl grouprepresented by b, c or d can include phenyl and naphthyl. A substituentwhich may be present on the aryl groups can include, for example,substituents similar to those which may be present on the aryl grouprepresented by Ar¹ and the like described above, and specific examplesof the aryl group having the substituent can include tolyl andmethoxyphenyl.

In the general formula (2), specific examples of the halogen atomrepresented by b, c or d can include, a fluorine atom and a chlorineatom.

Since the enamine compound represented by the general formula (2) hasparticularly high charge movability among the enamine compoundsrepresented by the general formula (1), an electrophotographicphotoreceptor having higher sensitivity and light responsivity can beobtained by using the enamine compound represented by the generalformula (2) as the charge transporting substance 13.

Further, since the enamine compound represented by the general formula(2) can be synthesized relatively easily and shows high yield among theenamine compounds represented by the general formula (1), it can bemanufactured at a reduced cost. Accordingly, the electrophotographicphotoreceptor 1 of this embodiment having the excellent characteristicsas described above can be manufactured at a reduced manufacturing cost.

Among the enamine compounds represented by the general formula (1),compounds having especially excellent in view of the characteristics,cost and productivity can include, for example, those in which each ofAr¹ and Ar² represents a phenyl group, Ar³ represents a phenyl group,tolyl group, p-methoxyphenyl group, biphenylyl group, naphthyl group orthienyl group, at least one of Ar⁴ and Ar⁵ represents a phenyl group,p-tolyl group, p-methoxyphenyl group, naphthyl group, thienyl group orthiazolyl group, and R¹, R², R³ and R⁴ each represents a hydrogen atom,and n represents 1.

Among the enamine compounds represented by the general formula (1), amore preferred compound is an enamine compound represented by thefollowing general formula (1a).

(in the formula, Ar¹ and Ar² each represents a phenyl group. Ar³represents a tolyl group, p-methoxyphenyl group, naphthyl group, or5-methyl-2-thienyl group, Ar⁴ represents a hydrogen atom, lower alkylgroup or phenyl group. Ar⁵ represents a phenyl group or p-methoxyphenylgroup. n represents an integer of 1 to 2).

Not only the compound of the general formula (1a) has high chargemovability but also the starting material is easily available, thesynthesis is easy, the yield is high, and it can be manufactured at areduced cost. Accordingly, an electrophotographic photoreceptor of theinvention having high sensitivity and excellent in the responsivity canbe manufactured at a reduced cost by using the compounds.

Specific examples of enamine compounds represented by the generalformula (1) can include, for example, Exemplified Compounds No. 1 to No.220, in Tables 1 to 32 described below, but they are not limited tothem. Further, in Tables 1 to 32, each of the exemplified compounds isrepresented by a group corresponding to each group of the generalformula (1). For example, Exemplified Compound No. 1 shown in Table 1 isan enamine compound represented by the following structural formula(1-1). In Tables 1 to 32, in a case of exemplifying those in which Ar⁴and Ar⁵ bond with each other by way of an atom or an atomic group toform a ring structure, carbon-carbon double bonds for bonding Ar⁴ andAr⁵, and ring structures formed by Ar⁴ and Ar⁵ together with the carbonatom of the carbon-carbon double bonds are shown in the column for Ar⁴to the column for Ar⁵.

TABLE 1 Compound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 1

H

1 CH═CH H H

2

H

1 CH═CH H H

3

H

1 CH═CH H —CH₃

4

H

1 CH═CH H H

5

H

1 CH═CH H H

6

H

1 CH═CH H H

7

H

1 CH═CH H —CH₃

TABLE 2 Compound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 8

H

1 CH═CH H H

9

H

1 CH═CH H —CH₃

10

H

1 CH═CH H —CH₃

11

H

1 CH═CH H H

12

H

1 CH═CH H H

13

H

1 CH═CH H H

14

H

1 CH═CH H H

TABLE 3 Com- pound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 15

H

1 CH═CH H H

16

H

1 CH═CH H —CH₃

17

H

1 CH═CH H H

18

H

1 CH═CH H —CH₃

19

H

1 CH═CH H H

20

H

1 CH═CH H H

21

H

1 CH═CH H H

TABLE 4 Compound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 22

H

1 CH═CH H H

23

H

1 CH═CH H —CH₃

24

H

1 CH═CH H —CH₃

25

H

1 CH═CH H H

26

H

1 CH═CH H H

27

H

1 CH═CH H H

28

H

1 CH═CH H

TABLE 5 Com- pound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 29

H

1 CH═CH H

30

H

1 CH═CH H

31

H

1 CH═CH H

32

H

1 CH═CH H

33

H

1 CH═CH H

34

H

1 CH═CH H

35

H

1 CH═CH H

TABLE 6 Compound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 36

H

1 CH═CH H

37

H

1 CH═CH H

38

H

1 CH═CH H

39

H

1 CH═CH —CH₃ H

40

H

1 CH═CH

H

41

H

1

H H

42

H

1

H H

TABLE 7 Compound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 43

H

1

H H

44

H

1

H H

45

H

1

H

46

H

2 CH═CH—CH═CH H H

47

H

2 CH═CH—CH═CH H H

48

H

2 CH═CH—CH═CH H —CH₃

49

H

2 CH═CH—CH═CH H —CH₃

TABLE 8 Com- pound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 50

H

2 CH═CH—CH═CH H —CH₃

51

H

2 CH═CH—CH═CH H —CH₃

52

H

2

H H

53

H

2

H H

54

H

3

H H

55

H

1 CH═CH H H

56

H

1 CH═CH H H

TABLE 9 Compound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 57

H

1 CH═CH H H

58

H

1 CH═CH H H

59

H

1 CH═CH H H

60

H

1 CH═CH H H

61

H

1 CH═CH H H

62

H

1 CH═CH H H

63

H

1 CH═CH H —CH₃

TABLE 10 Compound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 64

H

1 CH═CH H H

65

H

1 CH═CH H H

66

H

1 CH═CH H —CH₃

67

H

1 CH═CH H H

68

H

1 CH═CH H H

69

H

1 CH═CH H H

70

H

1 CH═CH H H

TABLE 11 Com- pound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 71

H

1 CH═CH H H

72

H

1 CH═CH H H

73

H

1 CH═CH H H

74

H

1 CH═CH H H

75

H

1 CH═CH H H

76

H

1 CH═CH H H

77

H

1 CH═CH H H

TABLE 12 Compound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 78

H

1 CH═CH H H

79

H

1 CH═CH H H

80

H

1 CH═CH H H

81

H

1 CH═CH H H

82

H

1 CH═CH H H

83

H

1 CH═CH H H

84

H

1 CH═CH H H

TABLE 13 Com- pound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 85

H

1 CH═CH H —CH₃

86

H

1 CH═CH H —CH₃

87

H

1 CH═CH H —CH₃

88

H

1 CH═CH H

89

H

1 CH═CH H

90

H

1 CH═CH H

91

H

1 CH═CH H

TABLE 14 Compound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 92

H

1 CH═CH H

93

H

1 CH═CH H

94

H

1 CH═CH H

95

H

1 CH═CH H

96

H

1 CH═CH H

97

H

1 CH═CH H

98

H

1 CH═CH H

TABLE 15 Compound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 99

H

1 CH═CH —CH₃ H

100

H

1 CH═CH

H

101

H

1

H H

102

H

1

H H

103

H

1

H H

104

H

1

H H

105

H

1

H

TABLE 16 Compound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 106

H

2 CH═CH—CH═CH H H

107

H

2 CH═CH—CH═CH H H

108

H

2 CH═CH—CH═CH H —CH₃

109

H

2 CH═CH—CH═CH H —CH₃

110

H

2 CH═CH—CH═CH H —CH₃

111

H

2 CH═CH—CH═CH H —CH₃

112

H

2 CH═CH—CH═CH H H

TABLE 17 Compound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 113

H

2

H H

114

H

2

H H

115

H

3

H H

116

H

1 CH═CH H H

117

H

1 CH═CH H H

118

H

1 CH═CH H H

119

H

1 CH═CH H H

TABLE 18 Compound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 120

H

1 CH═CH H H

121

H

1 CH═CH H H

122

H

1 CH═CH H H

123

H

1 CH═CH H —CH₃

124

H

1 CH═CH H

125

H

1 CH═CH H H

126

H

1 CH═CH H H

TABLE 19 Com- pound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 127

H

1 CH═CH H

128

H

1 CH═CH H H

129

H

1 CH═CH H H

130

H

1 CH═CH H

131

H

1 CH═CH H H

132

H

1 CH═CH H —CH₃

133

H

1 CH═CH H

TABLE 20 Com- pound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 134

H

1 CH═CH H H

135

H

1 CH═CH H H

136

H

1 CH═CH H

137

H

1 CH═CH H H

138

H

1 CH═CH H —CH₃

139

H

1 CH═CH H

140

H

1 CH═CH H H

TABLE 21 Com- pound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 141

H

1 CH═CH H H

142

H

1 CH═CH H —CH₃

143

H

1 CH═CH H H

144

H

1 CH═CH H —CH₃

145

H

1 CH═CH H —CH₃

146

H

1 CH═CH H H

147

H

1 CH═CH H —CH₃

TABLE 22 Compound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 148

H

1 CH═CH H H

149

H

1 CH═CH H —CH₃

150

H

1 CH═CH H H

151

H

1 CH═CH H —CH₃

152

H

1 CH═CH H —CH₃

153

H

1 CH═CH H —CH₃

154

H

1 CH═CH H H

TABLE 23 Com- pound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 155

H

1 CH═CH H —CH₃

156

H

1 CH═CH H —CH₃

157

H

1 CH═CH H —CH₃

158

H

1 CH═CH H H

159

H

1 CH═CH H

160

H

1 CH═CH H

161

H

1 CH═CH H

TABLE 24 Compound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 162

H

1 CH═CH H

163

H

1 CH═CH H

164

H

1 CH═CH H

165

H

2 CH═CH—CH═CH H H

166

H

2 CH═CH—CH═CH H —CH₃

167

H

2 CH═CH—CH═CH H —CH₃

168

H

3

H H

TABLE 25 Compound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 169

H

1 CH═CH H H

170

H

1 CH═CH H H

171

H

1 CH═CH H H

172

H

1 CH═CH H H

173

H

1 CH═CH H H

174

H

1 CH═CH H H

175

H

1 CH═CH H H

TABLE 26 Compound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 176

H

1 CH═CH H H

177

H

1 CH═CH H H

178

H

1 CH═CH H

179

H

1 CH═CH H H

180

H

1 CH═CH H —CH₃

181

H

1 CH═CH H

182

H

1 CH═CH H H

TABLE 27 Com- pound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 183

H

1 CH═CH H —CH₃

184

H

1 CH═CH H

185

H

1 CH═CH H H

186

H

1 CH═CH H H

187

H

1 CH═CH H

188

H

0 — H H

189

H

0 — H H

TABLE 28 Com- pound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 190

H

0 — H H

191

H

0 — H H

192

H

0 — H H

193

H

0 — H H

194

H

0 — H

195

H

0 — H H

196

H

0 — H H

TABLE 29 Com- pound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 197

H

0 — H H

198

H

0 — H H

199

H

0 — H H

200

H

0 — H H

201

H

0 — H

202

H

0 — H H

203

H

0 — H H

TABLE 30 Com- pound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 204

H

0 — H H

205

H

0 — H

206

H

0 — H H

207

H

0 — H H

208

H

0 — H

209

CH₃

1 CH═CH H H

210

CH₂CF₃

1 CH═CH H H

TABLE 31 Compound No. Ar¹ Ar² R¹ Ar³

n

R⁴ Ar⁴ Ar⁵ 211

CH(CH₃)₂

1 CH═CH H H

212

F

1 CH═CH H H

213

H

1 CH═CH H H

214

H

1 CH═CH H H

215

H

1 CH═CH H H

216

H

1 CH═CH H H

217

H

1 CH═CH H H

TABLE 32       Compound No.         Ar¹         Ar²         R¹        Ar³

218

H

219

H

220

H

Compound No. n

R⁴ Ar⁴ Ar⁵ 218 1 CH═CH H H

219 1 CH═CH H H

220 1 CH═CH H H

The enamine compound represented by formula (1) may be produced, forexample, as follows:

First, an aldehyde compound or a ketone compound represented by formula(3) is reacted with a secondary amine compound represented by formula(4) through dehydrating condensation to give an enamine intermediaterepresented by formula (5):

wherein Ar¹, Ar² and R¹ represent the same meanings as those defined informula (1).

wherein Ar³, a and m represent the same as those defined in formula (1).

wherein Ar¹, Ar², Ar³, R¹, a and m represent the same as those definedin formula (1).

The dehydrating condensation is effected, for example, as follows: analdehyde or ketone compound represented by formula (3) and a secondaryamine compound represented by formula (4) are, approximately in a ratioof 1/1 by mol, dissolved in a solvent of, for example, aromaticsolvents, alcohols or ethers to prepare a solution. Specific examples ofthe usable solvent are toluene, xylene, chlorobenzene, butanol anddiethylene glycol dimethyl ether. To the thus-prepared solution, addedis a catalyst, for example, an acid catalyst such as p-toluenesulfonicacid, camphorsulfonic acid or pyridinium-p-toluenesulfonate acid, andreacted under heat. The amount of the catalyst to be added is preferablyin a ratio by molar equivalent of from 1/10 to 1/1000 to the amount ofthe aldehyde or ketone compound represented by formula (3), morepreferably from 1/25 to 1/500, most preferably from 1/50 to 1/200.During the reaction, water is formed and it interferes with thereaction. Therefore, the water formed is removed out of the systemthrough azeotropic evaporation with the solvent used. As a result, theenamine intermediate represented by formula (5) is produced at highyield.

The enamine intermediate represented by formula (5) is formylatedthrough Vilsmeier reaction or is acylated through Friedel-Craftsreaction to give an enamine-carbonyl intermediate of the followinggeneral formula (6). The formylation through Vilsmeier reaction gives anenamine-aldehyde intermediate, a type of enamine-carbonyl intermediaterepresented by formula (6) where R⁵ is a hydrogen atom; and theacylation through Friedel-Crafts reaction gives an enamine-ketointermediate, a type of enamine-carbonyl intermediate represented byformula (6) where R⁵ is a group except hydrogen atom.

wherein R⁵ is R⁴ when n in formula (1) is 0, but is R² when n is 1, 2 or3; and Ar¹, Ar², Ar³, R¹, R², R⁴ a, m and n are the same as defined informula (1).

The Vilsmeier reaction is effected, for example, as follows: Phosphorusoxychloride and N,N-dimethylformamide (DMF), or phosphorus oxychlorideand N-methyl-N-phenylformamide, or phosphorus oxychloride andN,N-diphenylformamide are added to a solvent such asN,N-dimethylformamide or 1,2-dichloroethane to prepare a Vilsmeierreagent. 1.0 equivalent of an enamine intermediate represented byformula (5) is added to from 1.0 to 1.3 equivalents of the thus-preparedVilsmeier reagent, and stirred for 2 to 8 hours under heat at 60 to 110°C. Next, this is hydrolyzed with an aqueous alkaline solution such as 1to 8 N aqueous sodium hydroxide or potassium hydroxide solution. Thisgives an enamine-aldehyde intermediate, a type of enamine-carbonylintermediate represented by formula (6) where R⁵ is a hydrogen atom, athigh yield.

The Friedel-Crafts reaction is effected, for example, as follows: From1.0 to 1.3 equivalents of a reagent prepared from aluminum chloride andan acid chloride, and 1.0 equivalent of an enamine intermediaterepresented by formula (5) are added to a solvent such as1,2-dichloroethane, and stirred for 2 to 8 hours at −40 to 80° C. As thecase may be, the reaction system is heated. Next, this is hydrolyzedwith an aqueous alkaline solution such as 1 to 8 N aqueous sodiumhydroxide or potassium hydroxide solution. This gives an enamine-ketointermediate, a type of enamine-carbonyl intermediate represented byformula (6) where R⁵ is a group except hydrogen atom, at high yield.

Finally, the enamine-carbonyl intermediate represented by formula (6) isprocessed with a Wittig reagent of the following general formula (7-1)or (7-2) through Wittig-Horner reaction under basic condition to obtainan enamine compound represented by formula (1). In this step, when aWittig reagent represented by formula (7-1) is used, it gives an enaminecompound represented by formula (1) where n is 0; and when a Wittigreagent represented by formula (7-2) is used, it gives an enaminecompound represented by formula (1) where n is 1, 2 or 3.

wherein R⁶ represents an alkyl group which may have a substituent or anaryl group which may have a substituent; and Ar⁴ and Ar⁵ have the samemeanings as those defined in formula (1).

wherein R⁶ represents an alkyl group which may have a substituent or anaryl group which may have a substituent; n indicates an integer of from1 to 3; and Ar⁴, Ar⁵, R², R³ and R⁴ have the same meanings as thosedefined in formula (1).

The Wittig-Horner reaction is effected, for example, as follows: 1.0equivalent of an enamine-carbonyl intermediate represented by formula(6), from 1.0 to 1.20 equivalents of a Wittig reagent represented byformula (7-1) or (7-2), and from 1.0 to 1.5 equivalents of a metalalkoxide base such as potassium t-butoxide, sodium ethoxide or sodiummethoxide are added to a solvent such as toluene, xylene, diethyl ether,tetrahydrofuran (THF), ethylene glycol dimethyl ether,N,N-dimethylformamide or dimethylsulfoxide, and stirred for 2 to 8 hoursat room temperature or under heat at 30 to 60° C. This gives an enaminecompound represented by formula (1) at high yield.

As the enamine compound represented by the general formula (1), forexample, one or more of materials selected from the group consisting ofthe exemplified compounds shown in Table 1 to Table 32 is used alone oras a mixture.

The enamine compound represented by the general formula (1) may also beused with other charge transporting substance as a mixture. Other chargetransporting substance to be used in admixture with the enamine compoundrepresented by the general formula (1) can include, for example,carbazole derivatives, oxazole derivatives, oxadiazole derivatives,thiazole derivatives, thiadiazole derivatives, triazole derivatives,imidazole derivatives, imidazolone compound, imidazolidine derivatives,bisimidazolidine derivatives, styryl derivatives, hydrazone compound,polycyclic aromatic compound, indole derivatives, pyrazolinederivatives, oxazolone derivatives, benzimidazole derivatives,quinazoline derivatives, benzofuran derivatives, acrydine derivatives,phenadine derivatives, aminostylbene derivatives, triarylaminederivatives, triarylmethane derivatives, phenylene diamine derivatives,stylbene derivatives and benzidine derivatives. In addition, a polymerhaving a group generated from those compounds in a main chain or a sidechain, for example, poly-N-vinyl carbazole, poly-1-vinylpyrene andpoly-9-vinylanthracene and the like are included.

However, in order to attain particularly high charge transportability,it is preferred that the total amount of the charge transportingsubstance 13 is the enamine compound represented by the general formula(1).

As the antioxidant to be contained in the photosensitive layer 14,antioxidants usually utilized being added to resins, etc can be used asthey are, and for example, hindered phenol compounds, phosphoricantioxidants, organic sulfuric antioxidants, hydroquinone derivatives,paraphenylene diamine derivatives, or tocopherol compounds are used.

Among the antioxidants described above, hindered phenol compounds,phosphoric antioxidants and organic sulfuric antioxidants are preferablyused. When such antioxidants are used, decomposition and deteriorationof the enamine compound represented by the general formula (1) containedin the photosensitive layer 14 as the charge transporting substance 13can be suppressed particularly to further mitigate the fatiguedegradation upon repetitive use to further improve the durability of theelectrophotographic photoreceptor 1. In addition, stability of thecoating liquid upon forming the photosensitive layer 14 by coating canbe improved further, thereby enabling to further improve the stabilityof quality and the productivity of the electrophotographic photoreceptor1.

In this specification, the hindered phenol compound is a compound havinga hindered phenol structural unit, and the hindered phenol structuralunit is a structure unit derived from a phenol compound having a bulkyatomic group in the vicinity of a phenolic hydroxyl group. The bulkyatomic group includes, for example, branched alkyl groups, alicyclichydrocarbon groups, aryl groups and heterocyclic groups.

The hindered phenol structural unit is preferably represented by thefollowing general formula (I):

In the general formula (I), R¹¹ represents a branched alkyl group,linear alkyl group of 8 or more carbon atoms, unsaturated aliphatichydrocarbon group, cycloaliphatic hydrocarbon group, aryl group,heterocyclic group, multi-substituted silyl group, monovalent groupincluding a cyclic group or monovalent group including an alkyl group of4 or more carbon atoms. R¹², R¹³ and R¹⁴ each represents a hydrogenatom, halogen atom or monovalent organic residue, at least two of R¹²,R¹³ and R¹⁴ may bond with each other to form a ring structure. R¹⁵represents a hydrogen atom or monovalent organic residue.

In the general formula (I), as the branched alkyl group represented byR¹¹, those of 3 to 18 carbon atoms are preferred, and specific examplesthereof can include, for example, t-alkyl groups such as t-butyl,t-pentyl, and t-octyl, and s-alkyl groups such as s-butyl, s-octyl, ands-octadecyl.

As the linear alkyl group of 8 or more carbon atoms represented by R¹¹,those of 12 to 18 carbon atoms are preferred.

As the unsaturated aliphatic hydrocarbon group represented by R¹¹, thoseof 2 to 12 carbon atoms are preferred, and specific examples thereof caninclude, for example, alkenyl groups such as 2-propenyl, 1,3-butadienyl,2-pentenyl and 1,4-hexadienyl, alkynyl groups such as ethynyl and2-hexynyl, and aliphatic hydrocarbon groups having carbon-carbon doublebond and triple bond such as 2-pentene-4-inyl and 1-heptene-5-inyl.

As the cycloaliphatic hydrocarbon group represented by R¹¹, those of 5to 8 carbon atoms are preferred, and specific examples thereof caninclude, for example, cycloalkyl groups such as cyclopentyl, cyclohexyl,cycloheptyl and 1-methylcyclohexyl, cycloalkenyl groups such as2-cyclopenten-1-yl and 1-cyclohexenyl, cycloalkinyl groups such as2-cyclohexin-1-yl, and cycloaliphatic hydrocarbon group havingcarbon-carbon double bond and triple bond such as2-cyclodecen-5-in-1-yl.

Specific examples of the aryl group represented by R¹¹ can include, forexample, phenyl, naphthyl, anthryl and biphenylyl.

Specific examples of the heterocyclic group represented by R¹¹ caninclude, for example, thienyl, furyl, benzofuryl, benzothiophenyl andbenzothiazolyl.

Specific examples of the multiply-substituted silyl group represented byR¹¹ can include, for example, tri-substituted silyl group such astrimethylsilyl and triisopropylsilyl, and di-substituted silyl groupsuch as dimethylsilyl and diphenylsilyl.

The monovalent group containing a cyclic group represented by R¹¹preferably contains, as the cyclic group, the cycloaliphatic hydrocarbongroup, aryl group or cycloaliphatic group described above. Specificexamples of the monovalent group containing the cyclic group representedby R¹¹ can include, for example, aralkyl groups such as benzyl,phenetyl, 1-naphthylmethyl, and 1-methylbenzyl, phosphino groupsubstituted with an aryl group, such as phenylphosphino,diphenylphosphino, and ethylphenyl phosphino, cycloalkyl alkyl groupssuch as cyclohexylmethyl and 1-cyclohexyl-1-methylethyl, aryloxy groupssuch as phenoxy, arylthio groups such as thiophenoxy and alkyl groupssubstituted with a heterocyclic group such as furfuryl, pipelidiomethyl, and thienylmethyl.

The monovalent group containing an alkyl group of 4 or more carbon atomsrepresented by R¹¹, preferably contains alkyl groups of 4 to 18 carbonatoms as the alkyl group of 4 or more carbon atoms. Specific examples ofthe monovalent group containing an alkyl group of 4 or more carbon atomsrepresented by R¹¹ can include, for example, alkyl carbonyl amino groupssuch as heptylcarbonyl amino and N-methyloxyl carbonyl amino,alkylthioalkyl groups such as octylthiomethyl, decylthioethyl, andpentyl thioethyl, and alkoxy alkyl groups such as heptyloxymethyl,2-dodecylaoxyethy, and hexyloxyethyl.

In the general formula (I), the halogen atom represented by R¹², R¹³ orR¹⁴ can include, for example, a fluorine atom or chlorine atom.

The monovalent organic residue represented by R¹², R¹³ or R¹⁴ caninclude, for example, alkyl groups such as methyl, ethyl, t-butyl,t-pentyl, hexyl, and octyl, aryl groups such as phenyl, naphtyl,anthryl, and biphenylyl, aralkyl groups such as benzyl, phenetyl,1-naphthylmethyl, and 1-methylbenzyl, heterocyclic ring groups such aspyridyl, thienyl, furyl, benzofuryl, benzothiophenyl, benzothiazolyl,and N-indolyl, and amino groups such as diethyl amino, dimethyl amino,and diisopropyl amino. Further, hydroxyl group, alkoxy group, carboxylicacid group, acyl group, ester group, amido group, siloxane group, andsilyl group, etc. can also be included. The alkyl group represented byR¹², R¹³ or R¹⁴ preferably has from 1 to 40 carbon atoms.

The monovalent organic residue represented by R¹², R¹³ or R¹⁴ may have asubstituent, and the substituent can include, for example, an estergroup, carboxylic acid group, phospholic acid group, and thioethergroup.

In the general formula (I), the monovalent organic residue representedby R¹⁵ can include, for example, alkyl groups such as methyl, ethyl,propyl, hexyl and octyl, aryl groups such as phenyl, naphthyl, andanthlyl, aralkyl groups such as benzyl, phenetyl, and 1-naphthylmethyl,heterocyclic groups such as piridyl, thienyl, furyl, benzofuryl, andbenzothiophenyl, and acyl groups such as acryloyl and acetyl. The alkylgroup represented by R¹⁵ preferably has 1 to 40 carbon atoms, morepreferably, from 1 to 18 carbon atoms.

The hindered phenol compound may have two or more hindered phenolstructural units represented by the general formula (I) described above.In this case, the plurality of hindered phenol structural units may beidentical or different.

In a case where the hindered phenol compound contains a plurality ofhindered phenol structural units in this manner, the plurality ofhindered phenol structural units may be bonded directly or may be bondedby way of an atom or atomic group.

Specific examples of the atom for bonding the plurality of hinderedphenol structural units can include, for example, an oxygen atom, sulfuratom and carbon atom.

The atomic group for bonding the plurality of hindered phenol structuralunits can include, for example, polyvalent groups such as bivalent andtrivalent groups derived from saturated aliphatic hydrocarbons,unsaturated aliphatic hydrocarbons, aromatic hydrocarbons orheterocyclic compounds. Specific examples of the polyvalent groupderived from the saturated aliphatic hydrocarbons can include bivalentgroups, for example, alkylene groups such as methylene, ethylene, andpropylene, and alkylidene groups such as ethylidene, propylidene andbutylidene, and trivalent groups, for example, alkanylidene groups suchas 1-propanyl-3-ilydene and alkanetriyl groups such as 1,3,6-hexanetriyl. Specific examples of the polyvalent group derived fromunsaturated aliphatic hydrocarbon can include bivalent groups, forexample, alkenylene groups such as vinylene and propenylene,alkadienylene groups such as 1,3-butadienylene, and 1,4-hexadiethyleneand alkinylene groups such as 3-pentynylene and 2-hexynylene, andtrivalent groups, for example, alkenylidene groups such as2-pentenyl-5-ylidene. Specific examples of the polyvalent groups derivedfrom aromatic hydrocarbon can include, trivalent groups, for example,arylene groups such as phenylene, naphthylene, biphenylene and2,7-phenanetholylene and 1,3,5-benzenetriyl, and tetravalent groups suchas 1,4,5,8-anthracenetetrayl. Specific examples of the polyvalent groupsderived from the heterocyclic compound can include, for example,bivalent groups such as 3,5-pyridinediyl and 2,6-quinolinediyl,trivalent groups such as 1,3,5-triadine-2,4,6-triyl and1,3,5-triadine-2,4,6-trion-1,3,5-triyl, and tetravalent groups such as1,4,5,8-acridine tetrayl.

While specific examples of the hindered phenol compound can, forexample, include Exemplified Compounds HP-1 to HP-80 shown in Tables 33to 39, the hindered phenol compounds are not limited to them. In thefollowing description, t-Bu represents t-butyl group (—C(CH₃)₃, t-C₅H₁₁represents t-pentyl group (—C(CH₃)₂C₂H₅) and t-C₈H₁₇ represents t-octylgroup (—C(CH₃)₂C₅H₁₁).

TABLE 33 HP-1

HP-2

HP-3

HP-4

HP-5

HP-6

HP-7

HP-8

HP-9

HP-10

HP-11

HP-12

HP-13

HP-14

TABLE 34 HP-15

HP-16

HP-17

HP-18

HP-19

HP-20

HP-21

TABLE 35 HP-22

HP-23

HP-24

HP-25

HP-26

HP-27

TABLE 36 HP-28

HP-29

HP-30

HP-31

HP-32

HP-33

HP-34

HP-35

HP-36

HP-37

HP-38

HP-39

TABLE 37 HP-40

HP-41

HP-42

HP-43

HP-44

HP-45

HP-46

HP-47

HP-48

HP-49

HP-50

HP-51

HP-52

HP-53

TABLE 38 HP-54

HP-55

HP-56

HP-57

HP-58

HP-59

HP-60

HP-61

HP-62

HP-63

HP-64

HP-65

HP-66

HP-67

TABLE 39 HP-68

HP-69

HP-70

HP-71

HP-72

HP-73

HP-74

HP-75

HP-76

HP-77

HP-78

HP-79

HP-80

Among the hindered phenol compounds shown in Table 33 to Table 39,Exemplified Compound HP-1 shown in Table 33, namely, the hindered phenolcompound represented by the following structural formula (I-a) ispreferably used.

As a phosphoric antioxidant, while known compounds can be used, andspecific examples thereof can include, for example, ExemplifiedCompounds P-1 to P-47 shown in Tables 40 to 44, the phosphoricantioxidants are not limited to them.

TABLE 40 P-1 P(OCH₃)₃ P-2 P(OC₂H₅)₃ P-3 P(OC₄H₉)₃ P-4 P(OC₁₀H₂₁)₃ P-5P(OC₁₂H₂₅)₃ P-6 P(OC₁₃H₂₇)₃ P-7 P(OC₁₈H₃₇)₃ P-8 (H₂₅C₁₂O)₂P(O)H P-9(H₃₇C₁₈O)₂P(O)H P-10 P(SC₁₀H₂₁)₃ P-11 P(SC₁₂H₂₅)₃ P-12 P(SC₁₈H₃₇)₃ P-13

P-14

P-15

P-16

P-17

P-18

TABLE 41 P-19

P-20

P-21

P-22

P-23

P-24

P-25

P-26

P-27

P-28

P-29

P-30

TABLE 42 P-31

P-32

P-33

P-34

P-35

P-36

TABLE 43 P-37

P-38

P-39

P-40

P-41

P-42

TABLE 44 P-43

P-44

P-45

P-46

P-47

Exemplified Compound P-39 shown in Table 43 is commercially available,for example, as JPH-3800 (trade name of product, manufactured by JohokuChemical Co., Ltd.).

As the organic sulfuric antioxidant, while known compounds can be used,and specific examples thereof can include, for example, ExemplifiedCompounds S-1 to S-14 shown in Tables 45 and 46 described below, theorganic sulfuric antioxidants are not limited to them.

TABLE 45 S-1 S(C₈H₁₇)₂ S-2 S(C₁₂H₂₅)₂ S-3 S(C₁₆H₃₂)₂ S-4

S-5

S-6

S-7

S-8

TABLE 46 S-9

S-10

S-11

S-12

S-13

S-14

Further, as the light stabilizer, light stabilizers usually utilized bybeing added to resins can be generally used as they are. For example,hindered amine compounds, benzotriazole derivatives and benzophenonederivatives are used.

Among the light stabilizers described above, hindered amine compounds,benzotriazole derivatives, or benzophenone derivatives are preferablyused. When such light stabilizers are used, decomposition anddeterioration of the enamine compound represented by the general formula(I) contained in the photosensitive layer 14 as the charge transportingsubstance 13 are suppressed particularly to further mitigate fatiguedegradation upon repetitive use, and durability of theelectrophotographic photoreceptor 1 can be further improved. Inaddition, the stability of the coating liquid upon forming thephotosensitive layer 14 by coating is further improved, thereby enablingto further improve the stability of quality and the productivity of theelectrophotographic photoreceptor 1.

In this specification, “hindered amine compound” is a compound having ahindered amine structural unit, and the hindered amine structural unitis a structural unit derived from an amine compound having a bulkyatomic group in the vicinity of an amino nitrogen atom. The bulky atomicgroup can include, for example, a branched alkyl group, cycloaliphatichydrocarbon group, aryl group, and heterocyclic group. The hinderedamine structural unit may be either an aromatic amine type or aliphaticamine type, the aliphatic amine type being preferred.

The hindered amine structural unit is preferably represented by thefollowing general formula (II):

In the general formula (II), R¹⁶, R¹⁷, R¹⁸ and R¹⁹ each represents ahydrogen atom, alkyl group, aryl group, heterocyclic group or aralkylgroup. R²⁰ represents a hydrogen atom or a monovalent organic residue. Wrepresents an atomic group necessary for forming a ring structurecontaining an amino nitrogen atom. However, all of R¹⁶, R¹⁷, R¹⁸ and R¹⁹do not simultaneously represent a hydrogen atom.

In the general formula (II), as the alkyl group represented by R¹⁶, R¹⁷,R¹⁸ and R¹⁹, those of 1 to 18 carbon atoms are preferred. The alkylgroup represented by R¹⁶, R¹⁷, R¹⁶ and R¹⁹ may have a substituent, andthe substituent can include, for example, an aryl group, alkoxyl group,carboxylic acid group, amide group, halogen group and thioether group.

Specific examples of the aryl group represented by R¹⁶, R¹⁷, R¹⁸ and R¹⁹include, for example, phenyl, naphthyl, anthlyl and p-tolyl.

Specific examples of the heterocyclic group represented by R¹⁶, R¹⁷, R¹⁸and R¹⁹ can include, for example, thienyl, furyl, benzofuryl, andbenzothiophenyl.

Specific examples of the aralkyl group represented by R¹⁶, R¹⁷, R¹⁸ andR¹⁹ can include, for example, benzyl, phenetyl, 1-naphthylmethyl, and1-methylbenzyl.

The monovalent organic residue represented by R²⁰ can includes, forexample, alkyl groups such as methyl, ethyl, t-pentyl, hexyl, and octyl,acyl groups such as acetyl, propionyl and butyryl, aryl groups such asphenyl and naphthyl, aralkyl groups such as benzyl, phenetyl and1-naphtylmethyl, and heterocyclic groups such as pyridyl, thienyl,furyl, benzofuryl, and benzothiophenyl. The alkyl group represented byR²⁰ preferably has 1 to 18 carbon atoms.

In the general formula (II), the ring structure containing the aminonitrogen atom formed by W is preferably a five- or six-membered ring,and specific examples thereof can include, for example, each of therings of piperidine, piperazine, morpholine, pyrrolidine, imidazolidine,oxazolidine, thiazolidine, selenazolidine, pyroline, imidazoline,isoindoline, tetrahydroisoquinoline, tetrahydropyridine,dihydropyridine, dihydroisoquinoline, oxazoline, thiazoline,selenazoline, pyrrol, etc. Among them, while each of the rings ofpiperidine, piperazine and pyrolidine is particularly preferred. W hasone bonding chain in the general formula (II), it is not limitative, butmay also have two or more bonding chains.

The ring containing an amino nitrogen atom formed by W may have asubstituent, and the substituent can includes, for example, alkyl groupssuch as methyl, ethyl, and octyl, aryl groups such as phenyl andnaphthyl, aralkyl groups such as benzyl and phenetyl, heterocyclicgroups such as pyridyl, thienyl, furyl, benzofuryl, and benzothiophenyl,and amino groups such as methylamino, dimethylamino, and diphenylamino.In addition, ester groups, hydroxyl groups and silyl groups may also beincluded.

The hindered amine compound may have two or more hindered aminestructural units represented by the general formula (II) describedabove. In this case, the plurality of hindered amine structural unitsmay be identical or different with each other.

In a case where the hindered amine compound contains a plurality ofhindered amine structural units as described above, the plurality of thehindered amine structural units may be bonded directly or may be bondedby way of an atomic group.

Specific examples of the atom for bonding the plurality of hinderedamine structural units can include an oxygen atom, sulfur atom andcarbon atom.

Specific examples of the atomic group for bonding the plurality ofhindered amine structural units can include polyvalent groups, forexample, bivalent and trivalent polyvalent groups derived from saturatedaliphatic hydrocarbon, unsaturated aliphatic hydrocarbon, aromatichydrocarbon or heterocyclic compound. Specific examples of thepolyvalent group derived from the saturated aliphatic hydrocarbon caninclude bivalent groups, for example, alkylene groups such as methylene,ethylene, and propylene, and alkylidene groups such as ethylidene,propylidene and butylidene, and trivalent groups, for example,alkanylidene groups such as 1-propanyl-3-ilydene and alkanetriyl groupssuch as 1,3,6-hexane triyl. Specific examples of the polyvalent groupderived from unsaturated aliphatic hydrocarbons include bivalent groups,for example, alkenylene groups such as vinylene and propenylene,alkadienylene groups such as 1,3-butadienylene and 1,4-hexadiethyleneand alkinylene groups such as 3-pentynilene and 2-hexynylene, andtrivalent groups, for example, alkenylidene groups such as2-pentenyl-5-ylidene. Specific examples of the polyvalent groups derivedfrom aromatic hydrocarbon include trivalent groups, for example, arylenegroups such as phenylene, naphthylene, biphenylene and2,7-phenanetholylene and 1,3,5-benzene triyl, and tetravalent groupssuch as 1,4,5,8-anthracenetetrayl. Specific examples of the polyvalentgroups derived from heterocyclic compounds can include, for example,bivalent groups such as 3,5-pyridinediyl and 2,6-quinoline-diyl,trivalent groups such as 1,3,5-triadine-2,4,6-triyl, and tetravalentgroups such as 1,4,5,8-acridine-tetrayl.

The hindered amine compound may have the hindered phenol structuralunits described above in addition to the hindered amine structuralunits.

While specific examples of the hindered amine compound can include, forexample, Exemplified Compounds HA-1 to HA-15 shown in Tables 47 to 49described above, the hindered amine compounds are not limited to them.

TABLE 47 HA-1

HA-2

HA-3

HA-4

HA-5

HA-6

TABLE 48 HA-7

HA-8

HA-9

HA-10

TABLE 49 HA-11

HA-12

HA-13

HA-14

HA-15

Exemplified Compound HA-12 shown in Table 49 is commercially availableas TINUVIN 622 (trade name of product, manufactured by Ciba Geigy Co.,Ltd.). Exemplified Compound HA-14 is commercially available, forexample, as CHIMASSORB 944 (trade name of product, manufactured byNippon Ciba Geigy Co., Ltd.). Exemplified Compounds HA-15 iscommercially available, for example, as CHIMASSORB 119 (trade name ofproducts, manufactured by Nippon Ciba Geigy Co., Ltd.).

Among the hindered amine compounds shown in Tables 47 to 49, ExemplifiedCompound HA-3 shown in Table 47, namely, a hindered amine compoundrepresented by the following structural formula (II-a) is preferablyused.

While specific examples of the benzotriazole derivative can include, forexample, Exemplified Compounds TZ-1 to TZ-28 shown in the followingTables 50 to 52, the benzotriazole derivatives are not limited to them.

TABLE 50 TZ-1

TZ-2

TZ-3

TZ-4

TZ-5

TZ-6

TZ-7

TZ-8

TZ-9

TZ-10

TZ-11

TZ-12

TZ-13

TZ-14

TZ-15

TABLE 51 TZ-16

TZ-17

TZ-18

TZ-19

TZ-20

TZ-21

TZ-22

TZ-23

TZ-24

TZ-25

TZ-26

TABLE 52 TZ-27

TZ-28

In addition to the antioxidants shown in Table 33 to Table 46 and thelight stabilizers shown in Table 47 to Table 52, the compound that canbe used as the antioxidant or the light stabilizer include, for example,Exemplified Compounds X-1 to X-20 shown in the following Tables 53 toTable 55.

TABLE 53 X-1

X-2

X-3

X-4

X-5

X-6

X-7

X-8

TABLE 54 X-9

X-10

X-11

X-12

X-13

X-14

X-15

X-16

TABLE 55 X-17

X-18

X-19

X-20

The antioxidants and the light stabilizers shown in Table 33 to Table 55can be synthesized by various methods and are also available ascommercial products.

As the antioxidant and the light stabilizer, those selected from thegroup consisting of the exemplified compounds shown in Table 33 to Table55 are used each alone or two or more of them in admixture.

The antioxidant is contained in the light sensitive layer 14 preferablywithin a range of 0.1% by weight or more and 15% by weight or less, or,more preferably, within a range of 0.1% by weight or more and 5% byweight or less.

Further, the light stabilizer is contained in the light sensitive layer14 preferably within a range of 0.1% by weight or more and 10% by weightor less, or, more preferably, within a range of 0.1% by weight or moreand 5% by weight or less.

Further in a case where both of the antioxidant and the light stabilizerare contained in the photosensitive layer 14, the total content for theantioxidant and the light stabilizer in the photosensitive layer 14 is,preferably, 0.1% by weight or more and 20% by weight or less and, morepreferably, 0.1% by weight or more and 10% by weight or less.

A sufficient effect can be obtained for the improvement of thedurability of the electrophotographic photoreceptor 1 and theimprovement for the stability of the coating solution by selecting thecontent for the antioxidant, the content for the light stabilizer, orthe total content for the antioxidant and the light stabilizer in thephotosensitive layer 14. Further, lowering of the characteristics of theelectrophotographic photoreceptor 1 by the incorporation of theantioxidant and the light stabilizer can be minimized.

In a case where the content of the antioxidant, the content of the lightstabilizer and the total content of the antioxidant and the lightstabilizer in the photosensitive layer 14 is less than 0.1% by weight,no sufficient effect can be obtained for the improvement of thedurability of the photoreceptor 1 and the improvement for the stabilityof the coating solution. Further, in a case where the content of theantioxidant exceeds 15% by weight, the content of the light stabilizerexceeds 10% by weight or the total content of the antioxidant and thelight stabilizer exceeds 20% by weight in the photosensitive layer 14,this gives an undesired effect on the characteristics of thephotoreceptor. Accordingly, they are defined within the ranges describedabove.

The charge transporting layer 16 is formed in a state where the chargetransporting substance 13 containing the enamine compound represented bythe general formula (1) is bond to the binder resin 17. As the binderresin 17 for the charge transporting layer 16, those of excellentcompatibility with the charge transporting substance 13 are selected.Specific examples of the resin used for the binder resin 17 can include,for example, polymethyl methacrylate resin, polystyrene resin, vinylpolymer resin such as polyvinyl chloride and copolymer resin containingtwo or more of repetitive units constituting them, as well aspolycarbonate resin, polyester resin, polyester carbonate resin,polysulfone resin, phenoxy resin, epoxy resin, silicone resin,polyallylate resin, polyamide resin, polyether resin, polyurethaneresin, polyacryl amide resin, and phenol resin. Thermosetting resinsformed by partially crosslinking the resins described above may also beincluded. One of the resins may be used alone or two or more of them maybe used in admixture. Among the resins, since the polystyrene resins,polycarbonate resins, polyallylate resins, or polyphenylene oxides havea volume resistivity of 10¹³ Ω·cm or more and excellent in electricalinsulative property and also excellent in film property and potentialproperty, they are used particularly preferably for the binder resin 17.

The ratio A/B for the weight A of the charge transporting substance 13and the weight B for the binder resin 17 in the charge transportinglayer 16 is preferably from 10/12 to 10/30. In a case of using the knowncharge transporting substance, since the light responsivity maysometimes be lowered in a case where the ratio A/B is 10/12 or less byincreasing the ratio of the binder resin 17, the ratio A/B is about10/12. However, in the electrophotographic photoreceptor 1 of thisembodiment, since the enamine compound of high charge movabilityrepresented by the general formula (1) is used for the chargetransporting substance 13, even when the binder resin 17 is added at ahigher ratio than in the case of using the known charge transportingsubstance, at the ratio A/B of from 10/12 to 10/30, the lightresponsivity can be maintained. Accordingly, the printing resistance ofthe charge transporting layer 16 can be improved to improve thedurability of the electrophotographic photoreceptor 1 by increasing thecontent of the binder resin 17 in the charge transporting layer 16 withthe ratio A/B being at 10/12 to 10/30 without lowering the lightresponsivity.

In a case where the ratio A/B exceeds 10/12 and the ratio of the binderresin 17 is lowered, the printing resistance of the charge transportinglayer 16 is lowered and the amount of wear of the photosensitive layer14 is increased compared with a case where the ratio of the binder resin17 is higher. Further, in a case where the ratio A/B is less than 10/30and the ratio of the binder resin 17 is increased, since the viscosityof the coating solution increases to lower the coating speed in a caseof forming the charge transporting layer 16 by a dip coating method tobe described later, the productivity is worsened remarkably. Further, ina case where the amount of a solvent in the coating solution isincreased in order to suppress the increase of the viscosity of thecoating solution, brushing phenomenon occurs and clouding occurs in theformed charge transporting layer 16. Accordingly, the ratio A/B isdefined as 10/12 to 10/30.

For improving the film forming property, the flexibility and the surfacesmoothness, additives such as a plasticizer or a leveling agent may alsobe added as required to the charge transporting layer 16. Theplasticizer includes, for example, dibasic acid esters such as phthalateester, fatty acid ester, phosphate ester, chlorinated paraffin, andepoxy plasticizer. The leveling agent can include, for example, siliconetype leveling agent.

Further, for increasing the mechanical strength or improving theelectric property, fine particles of an inorganic compound or an organiccompound may also be added to the charge transport layer 16.

The charge transporting layer 16 is formed, for example, by dissolvingor dispersing a charge transporting substance 13 containing the enaminecompound represented by the general formula (1) and a binder resin 17 inan appropriate solvent to prepare a coating solution for chargetransporting layer and coating the outer circumferential surface of thecharge generating layer 15 with the obtained coating solution. In a caseof incorporating the antioxidant and the light stabilizer in the chargetransporting layer 16, a coating solution for charge transporting layeris prepared by dissolving the antioxidant and the light stabilizertogether with the charge transporting substance 13 and the binder resin17 in an appropriate solvent. Further, additives such as a plasticizer,leveling agent, or fine particles described above are added as requiredto the coating solution for charge transporting layer.

The solvent for the coating solution for charge transporting layer caninclude, for example, aromatic hydrocarbons such as benzene, toluene,xylene, and monochlorobenzene, halogenated hydrocarbons such asdichloromethane and dichloroethane, ethers such as tetrahydrofuran(THF), dioxane, and dimethoxymethyl ether, as well as aprotic polarsolvents such N,N-dimethylformamide are used each alone or in admixtureof two or more of them. Further, a solvent such as alcohols,acetonitrile, or methyl ethyl ketone may further be added to the solventdescribed above and used.

The coating method for the coating solution for charge transportinglayer includes, for example, a spraying method, bar coating method, rollcoating method, blade method, wringing method, or dip coating method.Among the coating methods described above, an optimal method can beselected while taking the physical property of the coating and theproductivity into consideration. Among the coating methods describedabove, the dip coating method is a method of dipping a substrate into acoating bath filled with a coating solution and then pulling up thesubstrate at a constant speed or at a gradually changing speed to form alayer on the surface of the substrate and, since the method isrelatively simple and excellent in view of the productivity and thecost, it has been often utilized in a case of manufacture anelectrophotographic photoreceptor and also often utilized in a case offorming the charge transporting layer 16.

The film thickness of the charge transporting layer 16 is, preferably, 5μm or more and 50 μm or less and, more preferably, 10 μm or more and 40μm or less. In a case where the film thickness of the chargetransporting layer 16 is less than 5 μm, the charge retainability on thesurface of the photoreceptor is lowered. In a case where the filmthickness of the charge transporting layer 16 exceeds 50 μm, resolutionpower of the photoreceptor 1 is lowered. Accordingly, it is defined as 5μm or more and 50 μm or less.

The charge generating layer 15 contains the charge generating substance12 as a main ingredient. The material effective as the charge generatingsubstance 12 can include azo pigments such as a monoazo pigment, bisazopigment, and trisazo pigment, indigo pigments such as indigo andthioindigo, perylene pigments such as peryleneimide and perylenic acidanhydride, polynuclear quinone pigments such as anthraquinone andpyrenequinone, phthalocyanine pigments such as metal phthalocyanines andnon-metal phthalocyanines, squarylium dyes, pyrylium salts, andthiopyrylium salts, triphenylmethane dyes, and inorganic materials suchas selenium and amorphous silicon. The charge generating substances maybe used each alone or two or more of them may be used in combination.

Among the charge generating substances described above, use ofoxotitanium phthalocyanine is preferred. Since oxotitaniumphthalocyanine is a charge generating substance having high chargegenerating efficiency and charge injecting efficiency, it generates agreat amount of charges by absorption of light and efficiently injectsthe generated charges, without accumulating them in the inside thereof,into the charge transporting substance 13. Further, since the enaminecompound of high charge movability represented by the general formula(1) is used for the charge transporting substance 13, the chargesgenerated from oxotitanium phthalocyanine as the charge generatingsubstance 12 by light absorption are efficiently injected into theenamine compound represented by the general formula (1) as the chargetransporting substance 13 and transported smoothly to the surface of thephotosensitive layer 14. Accordingly, electrophotographic photoreceptor1 of high sensitivity and high resolution power can be obtained by usingoxotitanium phthalocyanine as the charge generating substance 12.

The charge generating substance 12 may be used in combination withsensitizing dyes, for example, triphenylmethane dyes typicallyrepresented by methyl violet, crystal violet, night blue, and Victoriablue, acrydine dyes typically represented by erythrosin, rhodamine B,rhodamine 3R, acrydine orange, and fraveosin, thiazine dyes typicallyrepresents by methylene blue and methylene green, oxazine dyes typicallyrepresented by capri blue and merdora blue, cyanine dyes, stylyl dyes,pyrylium salt dyes, or thiopyrylium salt dyes.

The method of forming the charge generating layer 15 can include, forexample, a method of vacuum vapor depositing the charge generatingsubstance 12 on the outer circumferential surface of the conductivesubstrate 11, or a method of coating a coating solution for chargegenerating layer obtained by dispersing the charge generating substance12 in an appropriate solvent to the outer circumferential surface of theconductive substrate 11 is used. Among them, a method of dispersing thecharge generating substance 12 into a binder resin solution obtained bymixing a binder resin as a binder into an appropriate solvent by a knownmethod to prepare a coating solution for charge generating layer andcoating the outer circumferential surface of the conductive substrate 11with the obtained coating solution is used suitably. The method is to bedescribed below.

The binder resin used for the charge generating layer 15 can includethose resins, for example, polyester resin, polystyrene resin,polyurethane resin, phenol resin, alkyd resin, melamine resin, epoxyresin, silicone resin, acryl resin, methacryl resin, polycarbonateresin, polyarylate resin, phenoxy resin, polyvinyl butyral resin, andpolyvinyl formal resin, as well as copolymer resins containing two ormore of repetitive units constituting the resins described above.Specific examples of the copolymer resins include, for example, thoseinsulative resins such as vinyl chloride-vinyl acetate copolymer resin,vinyl chloride-vinyl acetate-maleic acid anhydride copolymer resin, andacrylonitrile-styrene copolymer resin. The binder resin is notrestricted to them but those resins used generally can be used as thebinder resin. The resins may be used each alone or two or more of themmay be used in admixture.

For the solvent of the coating solution for charge generating layer,halogenated hydrocarbons such as dichlomethane or dichloroethane,ketones such as acetone, methyl ethyl ketone or cyclohexanone, esterssuch as ethyl acetate or butyl acetate, ethers such as tetrahydrofuran(THF) or dioxane, alkyl ethers of ethylene glycol such as1,2-dimethoxyethane, aromatic hydrocarbons such as benzene, toluene orxylene, or aprotic polar solvent such as N,N-dimethylformamide andN,N-dimethylacetamide are used. Further, a mixed solvent formed bymixing two or more of the solvents can also be used.

As the blending ratio between the charge generating substance 12 and thebinder resin, it is preferred that the ratio of the charge generatingsubstance 12 is within a range from 10% by weight to 99% by weight. In acase where the ratio of the charge generating substance 12 is less than10% by weight, the sensitivity is lowered. In a case where the ratio ofthe charge generating substance 12 exceeds 99% by weight, since not onlythe film strength of the charge generating layer 15 is lowered but alsothe dispersibility of the charge generating substance 12 is lowered toincrease coarse particles and sometimes decrease the surface charges atthe portion other than the portion to be erased by exposure, thisincreases image defects, particularly, image fogging referred to as“black spot” where toners are deposited to the white back ground to formfine black spots. Accordingly, it is defined as from 10% by weight to99% by weight.

Before being dispersed in the binder resin solution, the chargegenerating substance 12 may previously be pulverized by a pulverizer.The pulverizer used for pulverization include, for example, a ball mill,sand mill, attritor, vibration mill, and supersonic dispersing machine.

The dispersing machine used upon dispersing the charge generatingsubstance 12 into the binder resin solution can include, for example, apaint shaker, ball mill, and sand mill. As the dispersion conditions,appropriate conditions are selected so as not to cause intrusion ofimpurities due to abrasion of members constituting the container ordispersing machine to be used.

In a case of incorporating the antioxidant and the light stabilizer inthe charge generating layer 15, the antioxidant and the light stabilizerare dissolved together with the charge generating substance 12 into anappropriate solvent or a binder resin solvent to prepare a coatingsolution for charge generating layer.

The coating method of the coating solution for charge generating layerincludes, for example, a spraying method, bar coating method, rollcoating method, blade method, wringing method, and dip coating method.Among the coating methods described above, since the dip coating methodis particularly excellent with various view points as described above,it has been often utilized also in a case of forming the chargegenerating layer 15. For the apparatus used for the dip coating method,a coating solution dispersing apparatus typically represented by asupersonic generation apparatus may be provided in order to stabilizethe dispersibility of the coating solution.

The film thickness of the charge generating layer 15 is, preferably,0.05 μm or more and 5 μm or less and, more preferably, 0.1 μm or moreand 1 μm or less. In a case where the film thickness of the chargegenerating layer 15 is less than 0.05 μm, the light absorptionefficiency is lowered to lower the sensitivity. In a case where the filmthickness of the charge generating layer 15 exceeds 5 μm, the chargetransfer in the charge generating layer constitutes a rate determiningstep in the process of erasing charges on the surface of thephotoreceptor to lower the sensitivity. Accordingly, it is defined as0.05 μm or more and 5 μm or less.

As described above, the photoconductive layer constituting thephotosensitive layer 14 comprises a stacked structure of the chargegenerating layer 15 and the charge transporting layer 16 formed asdescribed above. By sharing the charge generation function and thecharge transportation function to separate layers, since materialsoptimal to the charge generation function and the charge transportationfunction respectively can be selected for the material constituting eachof the layers, it is possible to obtain an electrophotographicphotoreceptor 1 having further higher sensitivity and having highdurability with further increased stability during repetitive use.

As the conductive material constituting the conductive substrate 11,metal materials, for example, elemental metals such as aluminum, copper,zinc, or titanium, as well as alloys such as aluminum alloys orstainless steels can be used. Further, with no particular restriction tosuch metal materials, polymeric materials such as polyethyleneterephthalate, nylon, or polystyrene, hard paper or glass in which metalfoils are laminated, metal materials are vapor deposited, or layers of aconductive compounds such as a conductive polymer, tin oxide, or indiumoxide are vapor deposited or coated on the surface thereof can also beused. The conductive materials are fabricated into a predetermined shapefor use. While the shape of the conductive substrate 11 is cylindricalin this embodiment, it is not restrictive but may be a circular columnarshape, sheet like shape, or endless belt shape.

The surface of the conductive substrate 11 may optionally be appliedwith an anodizing treatment, a surface treatment with chemicals or hotwater, a coloring treatment or a random reflection treatment, forexample, by surface roughening, within a range not affecting the picturequality. In the electrophotographic process using a laser as an exposuresource, since the wavelength of laser beams is coherent, an laser lightincident to and a light reflected from the photoreceptor may sometimescause interference, and interference fringes caused by the interferencemay sometimes appear on the images to result in image defects. Imagedefects by the interference of the laser light of the coherentwavelength can be prevented by applying the treatment described above tothe surface of the conductive substrate 11.

As has been described above, while the photosensitive layer 14 isconstituted with a photoconductive layer in which the charge generatinglayer 15 and the charge transporting layer 16 are stacked in this orderon the outer circumferential surface of the conductive substrate 11 inthis embodiment, this is not restrictive but it may be constituted witha photoconductive layer in which the charge transporting layer 16 andthe charge generating layer 15 are stacked in this order on the outercircumferential surface of the conductive substrate 11. FIG. 2 is across sectional view schematically showing the constitution of anelectrophotographic photoreceptor 2 as a second embodiment of theinvention. The electrophotographic photoreceptor 2 of this embodiment issimilar to the electrophotographic photoreceptor 1 of the firstembodiment, so that corresponding components will be denoted by the samereference numerals, and description thereof will be omitted.

In the electrophotographic photoreceptor 2, it is to be noted that anintermediate layer 18 is provided between a conductive substrate 11 anda photosensitive layer 14.

In a case where the intermediate layer 18 is not present between theconductive substrate 11 and the photosensitive layer 14, charges areinjected from the conductive substrate 11 to the photosensitive layer14, the chargeability of the photosensitive layer 14 is lowered, andsurface charges at a portion other than the portion to be eliminated byexposure are decreased to sometimes cause defects such as fogging toimages. Particularly, in a case of forming images by using a reversaldevelopment process, since toners are deposited to a portion where thesurface charges are decreased by exposure to form toner images, when thesurface charges are decreased by the factors other than exposure, thetoners are deposited to a white background and form minute black spotsto case fogging to the images referred to as black pots to sometimesdeteriorate a picture quality remarkably. That is, in a case where theintermediate layer 18 is not present between the conductive substrate 11and the photosensitive layer 14, chargeability is lowered in a minuteregion caused by the defects of the conductive substrate 11 or thephotosensitive layer 14 to sometimes cause fogging of images such asblack spots to result in remarkable image defects.

In the electrophotographic photoreceptor 2 of this embodiment, since theintermediate layer 18 is provided between the conductive substrate 11and the photosensitive layer 14 as described above, injection of chargesfrom the conductive substrate 11 to the photosensitive layer 14 can beprevented. Accordingly, lowering of the chargeability of thephotosensitive layer 14 can be prevented, decrease of the surfacecharges in the portion other than the portion to be eliminated byexposure can be suppressed and formation of defects to images such asfogging can be prevented.

In addition, the intermediate layer 18 may cover the surface defects ofthe conductive 11 to thereby make the substrate have a uniform surface,and the film-forming ability of the photosensitive layer 14 is thereforeenhanced. Further, the intermediate layer 15 prevents the photosensitivelayer 14 from being peeled off from the conductive substrate 11, and theadhesiveness between the conductive substrate 11 and the photosensitivelayer 14 is thereby enhanced.

The intermediate layer 18 may be a resin layer of various resinmaterials or an alumite layer.

The resin material to form the resin layer includes, for example,various resins such as polyethylene resins, polypropylene resins,polystyrene resins, acrylic resins, polyvinyl chloride resins, polyvinylacetate resins, polyurethane resins, epoxy resins, polyester resins,melamine resins, silicone resins, polyvinyl butyral resins and polyamideresins; copolymer resins containing at least two repetitive units ofthese resins; casein, gelatin, polyvinyl alcohol, and ethyl cellulose.Of those, especially preferred are polyamide resins. Also preferred arealcohol-soluble nylon resins. Preferred examples of the alcohol-solublenylon resins are so-called copolymer nylons prepared throughcopolymerization with 6-nylon, 6,6-nylon, 6,10-nylon, 11-nylon, 2-nylon,or 12-nylon; and chemically-modified nylon resins such asN-alkoxymethyl-modified nylon and N-alkoxyethyl-modified nylon.

The intermediate layer 18 may contain particles such as metal oxideparticles or the like. The particles may control the volume resistivityof the intermediate layer 15 and will be effective for furtherpreventing the charge injection from the conductive substrate 11 to thephotosensitive layer 14, and, in addition, they may ensure the electricproperties of the photoreceptors under different conditions.

The metal oxide particles may be, for example, particles of titaniumoxide, aluminum oxide, aluminum hydroxide or tin oxide.

The intermediate layer 18 is formed, for example, by dissolving ordispersing the resin described above in an appropriate solvent toprepare a coating liquid for intermediate layer, and coating the outercircumferential surface of the conductive substrate 11 with the coatingliquid. In a case of particles such as metal oxide particles describedabove in the intermediate layer 18, for example, the intermediate layer18 can be formed by dispersing the particles in a resin solutionobtained by dissolving the resin described above in an appropriatesolvent to prepare a coating liquid for intermediate layer, and coatingthe surface of the conductive substrate 11 with the coating liquid.

For the solvent of the coating liquid for intermediate layer, water orvarious kinds of organic solvents or mixed solvents of them may be used.For example, a single solvent of water, methanol, ethanol or butanol ora mixed solvent such as of water and alcohol, two or more kinds ofalcohols, acetone or dioxolane and alcohols, and chlorine type solventsuch as dichloroethane, chloroform or trichloroethane and alcohols areused. Among the solvents, non-halogen organic solvents are preferablyused in view of the global environment.

For the method of dispersing the particles in a resin solution, ordinarymethods including the use of using a ball mill, sand mill, attritor,vibration mill, or ultrasonic wave dispersing machine can be used.

In the coating liquid for intermediate layer the ratio of the totalcontent C of the resin and the metal oxide to the solvent content D ofthe coating liquid, C/D by weight preferably falls between 1/99 and40/60, more preferably between 2/98 and 30/70. The ratio by weight ofthe content of the resin to the content of the metal oxide (resin/metaloxide), preferably falls between 90/10 and 1/99, more preferably between70/30 and 5/95.

For applying the coating liquid for intermediate layer to the substrate,employable is a method of spraying, bar coating, roll coating, bladecoating, ring coating or dipping. As so mentioned hereinabove, a dippingmethod is relatively simple and favorable in point of the productivityand the production costs, and it is much utilized in forming theintermediate layer 18.

The thickness of the intermediate layer 18 is preferably from 0.01 μm to20 μm, more preferably from 0.05 μm to 10 μm. When the intermediatelayer 18 is thinner than 0.01 μm, it could not substantially function asan intermediate layer 18, or that is, it could not cover the defects ofthe conductive substrate 11 to form a uniform surface, and it could notprevent the charge injection from the conductive substrate 11 to thephotosensitive layer 14. As a result, the chargeability of thephotosensitive layer 14 will lower. When the intermediate layer 18 isthicker than 20 μm and when such a thick intermediate layer 18 is formedaccording to a dipping method, the intermediate layer 18 will bedifficult to form and, in addition, a uniform photosensitive layer 14could not be formed on the intermediate layer 18, and the sensitivity ofthe photoreceptor will lower. Therefore, such a thick layer isunfavorable for the intermediate layer 18. Accordingly, a preferredrange for the thickness of the intermediate layer 18 is defined as 0.01μm or more and 20 μm or less.

FIG. 3 is a cross sectional view schematically showing the constitutionof an electrophotographic photoreceptor 3 according to a thirdembodiment of the invention. The electrophotographic photoreceptor 3 ofthis embodiment is similar to the electrophotographic photoreceptor 2 ofthe second embodiment, so that corresponding components will be denotedby the same reference numerals, and description thereof will be omitted.

In the electrophotographic photoreceptor 3, it is to be noted that thephotosensitive layer 140 is constituted with a single layer containing acharge generating substance 12 and a charge transporting substance 13.That is, the electrophotographic photoreceptor 3 is a single layer typephotoreceptor.

Like the first embodiment and the second embodiment, the enaminecompound represented by the general formula (1) is used for the chargetransporting substance 13 in this embodiment. Further, thephotosensitive layer 140 contains at least one of the antioxidant andthe light stabilizer. Accordingly, like in the first and secondembodiments, it is possible to obtain a highly reliableelectrophotographic photoreceptor 3 having high chargeability,sensitivity and light responsivity, not suffering from lowering of thecharacteristics described above even in a case where it is used under alow temperature circumstance or in a high speed electrophotographicprocess, or it is exposed to light, stable against an active gas such asozone or NOx, UV-rays and heat, with less fatigue deterioration of thefilm after repetitive use.

The content of the antioxidant, the content of the light stabilizer, andthe total content of the antioxidant and the light stabilizer in thephotosensitive layer 140 are identical with the content of theantioxidant, the content of the light stabilizer, and the total contentof the antioxidant and the light stabilizer in the photosensitive layer14 of the first embodiment.

The photosensitive layer 140 is formed by the same method as for thecharge transporting layer 16 disposed in the electrophotographicphotoreceptor 1 of the first embodiment. For example, the photosensitivelayer 140 can be formed by dissolving or dispersing the chargegenerating substance 12, the charge transporting substance 13 containingthe enamine compound represented by the general formula (1), the binderresin 17, at least one of the antioxidant and the light stabilizer and,if necessary, the additives described above into an appropriate solventlike that of the coating solution for charge transporting layer toprepare a coating solution of photosensitive layer and coating the outercircumferential surface of an intermediate layer 18 with the coatingsolution for photosensitive layer, for example, by a dip coating method.

The ratio A′/B′ for the weight A′ of the charge transporting substance13 and the weight B′ for the binder resin 17 in the photosensitive layer140 is preferably from 10/12 to 10/30 in the same manner as the ratioA/B for the weight A of the charge transporting substance 13 and for theweight B of the binder resin 17 in the charge transporting layer 16 ofthe first embodiment.

The thickness of the photosensitive layer 140 is, preferably, from 5 μmor more and 100 μm or less and, more preferably, 10 μm or more and 50 μmor less. In a case where the thickness of the photosensitive layer 140is less than 5 μm, the charge retainability on the surface of thephotoreceptor is lowered. In a case where the thickness of thephotosensitive layer 140 exceeds 100 μm, the productivity is lowered.Accordingly, it is defined as 5 μm or more and 100 μm or less.

For the photosensitive layer 14 or 140, disposed to theelectrophotographic photoreceptor 1, 2, or 3 for the first to thirdembodiments described above, one or more of electron accepting materialsor dyes may also be added in order to improve the sensitivity andsuppress the increase of the residual potential and fatigue duringrepetitive use.

As the electron accepting material, acid anhydrides, for example,succinic acid anhydride, maleic acid anhydride, phthalic acid anhydride,and 4-chloronaphthalic acid anhydride, cyano compounds such astetracyanoethylene and terephthal malone dinitrile, aldehydes such as4-nitrobenzaldehyde, anthraquinones such as anthraquinone and1-nitroanthraquinone, polynuclear or heterocyclic nitro compounds suchas 2,4,7-trinitrofluorenone and 2,4,5,7-tetranitrofuorenone, or electronaccepting materials such as diphenoxy compounds can be used. Further,the polymerized electron accepting materials of them may also be used.

As the dye, for example, organic photoconductive compounds such asxanthene dye, thiazine dye, triphenylmethane dye, quinoline pigment orcopper phthalocyanine can be used. Further, the organic photocnductivecompounds function as the optical sensitizer.

Various layer constitutions can be adopted for the electrophotographicphotoreceptor according to the invention not being restricted to theconstitutions of the electrophotographic photoreceptors 1, 2, 3 of thefirst to third embodiments described above.

For example, in the electrophotographic photoreceptors 1, 2, and 3 ofthe first to third embodiments, a photosensitive layer 14 constitutedwith a photoconductive layer in which the charge generating layer 15 andthe charge transporting layer 16 are stacked, or a photosensitive layer140 constituted with a single photoconductive layer containing thecharge generating substance 12 and the charge transporting substance 13are provided, they are not limitative but a photosensitive layer formedby stacking a surface protective layer further on the photoconductivelayer may also be provided.

By disposing the surface protective layer on the photoconductive layer,the printing resistance of the photosensitive layer can be improved and,at the same time, the undesired chemical effects of the active gas suchas ozone or nitrogen oxide (NOx) generated by corona discharge uponcharging the surface of the photoreceptor can be prevented further. Forthe surface protective layer, a layer formed of, for example, a resin,inorganic filler-containing resin or an inorganic oxide may be used.

In a case where the photosensitive layer has a surface protective layerstacked on the photoconductive layer, the antioxidant or the lightstabilizer may be contained either in the photoconductive layer or inthe surface protective layer and may be contained in both of thephotoconductive layer and the surface protective layer.

As an image forming apparatus of a fourth embodiment according to theinvention, an image forming apparatus 100 having the electrophotographicphotoreceptor 1 (photoreceptor 1) of the first embodiment describedpreviously is illustrated. The image forming apparatus of the inventionis not restricted to the contents of the following descriptions. FIG. 4is a side elevational view for the arrangement schematically showing theconstitution of the image forming apparatus 100.

The image forming apparatus 100 includes a photoreceptor 1 rotatablysupported to an apparatus main body (not shown) and driving means (notshown) for rotationally driving the photoreceptor 1 around a rotationalaxis 44 in a direction of an arrow 41. The driving means has, forexample, a motor as a source of power and rotationally drives thephotoreceptor 1 at a predetermined circumferential speed by transmittingthe power from the motor by way of gears (not shown) to a supportconstituting the core of the photoreceptor 1.

Around the periphery of the photoreceptor 1, a charger 32, exposuremeans (not shown), a developing device 33, a transfer device 34, and acleaner 36 are arranged in this order from the upstream to thedownstream in the rotational direction of the photoreceptor 1 shown byan arrow 41. The cleaner 36 is disposed together with a chargeelimination lamp (not shown).

The charger 32 is charging means for charging the outer circumferentialsurface 43 of the photoreceptor 1 to a predetermined potential. Thecharger 32 is, for example, contact type charging means such as of aroller charging system.

The exposure means has, for example, a semiconductor laser as a lightsource and applies exposure in accordance with image information to thecharged outer circumferential surface 43 of the photoreceptor 1 byirradiating the outer circumferential surface 43 of the photoreceptor 1situated between the charger 32 and the developing device 33, with alight 31 such as a laser beam outputted from a light source.

The developing device 33 is developing means for developingelectrostatic latent images formed by exposure at the outercircumferential surface 43 of the photoreceptor 1 by a developer, andhas a developing roller 33 a for supplying a toner to the outercircumferential surface 43 of the photoreceptor 1 disposed being opposedto the photoreceptor 1, and a casing 33 b for rotatably supporting thedeveloping roller 33 a around a rotational axis in parallel with therotational axis 44 of the photoreceptor 1 and housing the developercontaining the toner in the inner space thereof.

The transfer device 34 is transfer means for transferring toner imagesas visible images formed by development at the outer circumferentialsurface 43 of the photoreceptor 1 by conveying means (not shown) onto atransfer paper 51 as a recording medium supplied by conveying means (notshown) in a direction of an arrow 42 to a position between thephotoreceptor 1 and the transfer device 34. The transfer device 34 has,for example, charging means, which is non-contact type transfer meansfor giving electric charges at a polarity opposite to that of the tonerto the transfer paper 51 and thereby transferring the toner images tothe transfer paper 51.

The cleaner 36 is cleaning means for removing and recovering a tonerremained on the outer circumferential surface 43 of the photoreceptor 1after the transfer operation by the transfer device 34 and has acleaning blade 36 a for peeling the toner remaining on the outercircumferential surface 43 of the photoreceptor 1 from the outercircumferential surface 43 and a recovery casing 36 b for containing thetoner peeled by the cleaning blade 36 a.

Further, a fixing device 35 as fixing means for fixing transferredimages is provided in a direction in which the transfer paper 51 isconveyed after passage between the photoreceptor 1 and the transferdevice 34. The fixing device 35 has a heating roller 35 a having heatingmeans (not shown), and a press roller 35 b opposed to the heating roller35 a and pressed by the heating roller 35 a to form an abutment portion.

The operation by the image forming apparatus 100 is to be described. Atfirst, when the photoreceptor 1 is driven rotationally by thephotoreceptor driving means in the direction of the arrow 41, the outercircumferential surface 43 of the photoreceptor 1 is uniformly chargedto a predetermined positive or negative potential by the charger 32which is disposed to the upstream of the focusing point of a light 31from the exposure means in the rotational direction of the photoreceptor1.

Then, the outer circumferential surface 43 of the photoreceptor 1 isirradiated with the light 31 from the exposure means. The light 31 fromthe light source is scanned repetitively in the longitudinal directionof the photoreceptor 1 as the main scanning direction. Exposure isapplied in accordance with the image information to the outercircumferential surface 43 of the photoreceptor 1 by rotationallydriving the photoreceptor 1 and scanning the light 31 from the lightsource repetitively. The surface charges at the portion being irradiatedwith the light 31 are eliminated by the exposure, and a difference iscaused between the surface potential at a portion being irradiated withthe light 31 and the surface potential at a portion being not irradiatedwith the light 31, to form electrostatic latent images to the outercircumferential surface 43 of the photoreceptor 1.

Then, a toner is supplied from the developing roller 33 a of thedeveloping device 33 disposed to the downstream of the focusing point ofthe light 31 from the light source in the rotational direction of thephotoreceptor 1 to the outer circumferential surface 43 of thephotoreceptor 1 formed with the electrostatic latent images. Thus theelectrostatic latent images are developed and toner images are formed onthe outer circumferential surface 43 of the photoreceptor 1.

Further, in synchronization with the exposure to the photoreceptor 1,the transfer paper 51 is supplied by the conveying means to a positionbetween the photoreceptor 1 and the transfer device 34 in the directionof the arrow 42. When the transfer paper 51 is supplied between thephotoreceptor 1 and the transfer device 34, the transfer device 34 giveselectric charges at a polarity opposite to the polarity of the toner tothe transfer paper 51. Thus, toner images formed on the outercircumferential surface 43 of the photoreceptor 1 are transferred on thetransfer paper 51.

The transfer paper 51 transferred with the toner images is conveyed bythe conveying means to the fixing device 35 and heated and pressurizedupon passage through an abutment portion between the heating roller 35 aand the pressure roller 35 b of the fixing device 35. Thus, the tonerimages on the transfer paper 51 are fixed to form firm images on thetransfer paper 51. The transfer paper 51 thus formed with the images isdischarged by the conveying means to the outside of the image formingapparatus 100.

On the other hand, the toner remaining on the outer circumferentialsurface 43 of the photoreceptor 1 after the transfer operation by thetransfer device 34 is separated by the cleaning blade 36 a of thecleaner 36 from the outer circumferential surface 43 of thephotoreceptor 1 and recovered in the recovery casing 36 b. The chargeson the outer circumferential surface 43 of the photoreceptor 1 thusremoved with the toner are thus eliminated by a light from the chargeelimination lamp, by which the electrostatic latent images on the outercircumferential surface 43 of the photoreceptor 1 are erased. Then thephotoreceptor 1 is further driven rotationally and a series ofoperations starting from the charging of the photoreceptor 1 arerepeated. As described above, images are formed continuously.

Since the photoreceptor 1 equipped in the image forming apparatus 100has the photosensitive layer 14 containing the enamine compoundrepresented by the general formula (1) as the charge transportingsubstance 13 and further containing at least one of the antioxidant andthe light stabilizer, it has high chargeability, sensitivity, and lightresponsivity, does not suffer from lowering of the characteristicsdescribed above even in a case when it is used under a low temperaturecircumstance or in a high speed electrophotographic process, is stableagainst an active gas such as ozone or NOx, UV-rays and heat asdescribed above, suffers from less fatigue degradation upon repetitiveuse and has high reliability. Accordingly, a highly reliable imageforming apparatus 100 capable of providing high quality images stablyfor a long time under various circumstances can be obtained. Further,since the electrophotographic photoreceptor 1 of the invention does notsuffer from lowering of the characteristics described above even in acase when it is exposed to light, it is possible to prevent lowering ofthe image quality caused by exposure of the electrophotographicphotoreceptor 1 to the light during maintenance or the like to improvethe reliability of the image forming apparatus 100.

As has been described above, while the image forming apparatus 100 ofthis embodiment has an electrophotographic photoreceptor 1 of the firstembodiment, this is not restrictive and it may have theelectrophotographic photoreceptor 2 of the second embodiment, theelectrophotographic photoreceptor 3 of the third embodiment or anelectrophotographic photoreceptor having a layer constitution differentfrom the electrophotographic photoreceptor of the first to thirdembodiments 1, 2, and 3.

Further, while the charger 32 is contact type charging means, it is notrestrictive but may also be a non-contact type charging means such as acorona discharging system.

Further, while the transfer device 34 is non-contact type transfer meanshaving the charging means, for transferring toner images on the transferpaper 51 by applying charges at a polarity opposite to that of the tonerto the transfer paper 51, this is not restrictive but may also becontact type transfer means having a roller, for transferring tonerimages on the transfer paper 51 by bringing the transfer paper 51 andthe electrophotographic photoreceptor 1 in press contact with each otherby using the rollers.

EXAMPLES

The present invention is to be describe further specifically by way ofexamples but the invention is not restricted to them.

Production Example 1 Production of Compound No. 1 Production Example 1-1Production of Enamine Intermediate

23.3 g (1.0 equivalent) of N-(p-tolyl)-α-naphthylamine of the followingstructural formula (8), 20.6 g (1.05 equivalents) ofdiphenylacetaldehyde of the following structural formula (9), and 0.23 g(0.01 equivalent) of DL-10-camphorsulfonic acid were added to 100 ml oftoluene and heated, and these were reacted for 6 hours while theside-product, water was removed out of the system through azeotropicdistillation with toluene. After thus reacted, the reaction solution wasconcentrated to about 1/10, and gradually and dropwise added to 100 mlof hexane that was vigorously stirred, and this gave a crystal. Thecrystal was taken out through filtration, and washed with cold ethanolto obtain 36.2 g of a pale yellow powdery compound.

Thus obtained, the compound was analyzed through liquidchromatography-mass spectrometry (LC-MS), which gave a peak at 412.5corresponding to the molecular ion [M+H]⁺ of an enamine intermediate(calculated molecular weight: 411.20) of the following structuralformula (10) with a proton added thereto. This confirms that thecompound obtained herein is the enamine intermediate represented byformula (10) (yield: 88%). In addition, the data of LC-MS furtherconfirm that the purity of the enamine intermediate obtained herein is99.5%.

As in the above, the dehydrating condensation ofN-(p-tolyl)-α-naphthylamine, a secondary amine represented by formula(8), and diphenylacetaldehyde, an aldehyde compound represented byformula (9) gives the enamine intermediate represented by formula (10).

Production Example 1-2 Production of Enamine-Aldehyde Intermediate

9.2 g (1.2 equivalents) of phosphorus oxychloride was gradually added to100 ml of anhydrous N,N-dimethylformamide (DMF) and stirred for about 30minutes to prepare a Vilsmeier reagent. 20.6 g (1.0 equivalent) of theenamine intermediate represented by formula (10) obtained in ProductionExample 1-1 was gradually added to the solution with cooling with ice.Next, this was gradually heated up to 80° C., and stirred for 3 hourswhile kept heated at 80° C. After thus reacted, the reaction solutionwas left cooled, and then this was gradually added to 800 ml of cold 4 Naqueous sodium hydroxide solution to form a precipitate. Thus formed,the precipitate was collected through filtration, well washed withwater, and then recrystallized from a mixed solvent of ethanol and ethylacetate to obtain 20.4 g of an yellow powdery compound.

Thus obtained, the compound was analyzed through LC-MS, which gave apeak at 440.5 corresponding to the molecular ion [M+H]⁺ of anenamine-aldehyde intermediate (calculated molecular weight: 439.19) ofthe following structural formula (11) with a proton added thereto. Thisconfirms that the compound obtained herein is the enamine-aldehydeintermediate represented by formula (11) (yield: 93%). In addition, thedata of LC-MS further confirm that the purity of the enamine-aldehydeintermediate obtained herein is 99.7%.

As in the above, the formylation of the enamine intermediate representedby formula (10) through Vilsmeier reaction gives the enamine-aldehydeintermediate represented by formula (11).

Production Example 1-3 Production of Compound No. 1

8.8 g (1.0 equivalent) of the enamine-aldehyde intermediate representedby formula (11) obtained in Production Example 1-2, and 6.1 g of diethylcinnamylphosphonate of the following structural formula (12) weredissolved in 80 ml of anhydrous DMF, and 2.8 g (1.25 equivalents) ofpotassium t-butoxide was gradually added to the solution at roomtemperature, then heated up to 50° C., and stirred for 5 hours whilekept heated at 50° C. The reaction mixture was left cooled, and pouredinto excess methanol. The deposit was collected, and dissolved intoluene to prepare a toluene solution thereof. The toluene solution wastransferred into a separating funnel and washed with water, and theorganic layer was taken out. Thus taken out, the organic layer was driedwith magnesium sulfate. Solid matter was removed from the thus-driedorganic layer, which was then concentrated and subjected to silica gelcolumn chromatography to obtain 10.1 g of an yellow crystal.

Thus obtained, the crystal was analyzed through LC-MS, which gave a peakat 540.5 corresponding to the molecular ion [M+H]⁺ of the intendedenamine compound, Compound No. 1 in Table 1 (calculated molecularweight: 539.26) with a proton added thereto.

The nuclear magnetic resonance (NMR) spectrum of the crystal in heavychloroform (chemical formula: CDCl₃) was measured, and this spectrumsupports the structure of the enamine compound, Compound No. 1. FIG. 5is the ¹H-NMR spectrum of the product in this Production Example 1-3,and FIG. 6 is an enlarged view of the spectrum of FIG. 5 in the range offrom 6 ppm to 9 ppm. FIG. 7 is the ¹³C-NMR spectrum in ordinarymeasurement of the product in Production Example 1-3, and FIG. 8 is anenlarged view of the spectrum of FIG. 7 in the range of from 110 ppm to160 ppm. FIG. 9 is the ¹³C-NMR spectrum in DEPT135 measurement of theproduct in Production Example 1-3, and FIG. 10 is an enlarged view ofthe spectrum of FIG. 9 in the range of from 110 ppm to 160 ppm. In FIG.5 to FIG. 10, the horizontal axis indicates the chemical shift δ (ppm)of the compound analyzed. In FIG. 5 and FIG. 6, the data written betweenthe signals and the horizontal axis are relative integral values of thesignals based on the integral value, 3, of the signal indicated by thereference numeral 500 in FIG. 5.

The data of LC-MS and the NMR spectrometry confirm that the crystalobtained herein is the enamine compound, Compound No. 1 (yield: 94%). Inaddition, the data of LC-MS further confirm that the purity of theenamine compound, Compound No. 1 obtained herein is 99.8%.

As in the above, the Wittig-Horner reaction of the enamine-aldehydeintermediate represented by formula (11) and the Wittig reagent, diethylcinnamylphosphonate represented by formula (12) gives the enaminecompound, Compound No. 1 shown in Table 1.

Production Example 2 Production of Compound No. 61

In the same manner as in Production Example 1 except that 4.9 g (1.0equivalent) of N-(p-methoxyphenyl)-α-naphthylamine was used in place of23.3 g (1.0 equivalent) of N-(p-tolyl)-α-naphthylamine represented byformula (8), an enamine intermediate was produced (yield: 94%) throughdehydrating condensation and an enamine-aldehyde intermediate wasproduced (yield: 85%) through Vilsmeier reaction, and this was furthersubjected to Wittig-Horner reaction to obtain 7.9 g of an yellow powderycompound. The equivalent relationship between the reagent and thesubstrate used in each reaction was the same as that in ProductionExample 1.

Thus obtained, the compound was analyzed through LC-MS, which gave apeak at 556.7 corresponding to the molecular ion [M+H]⁺ of the intendedenamine compound, Compound No. 61 in Table 9 (calculated molecularweight: 555.26) with a proton added thereto.

The NMR spectrum of the compound in heavy chloroform (CDCl₃) wasmeasured, and this spectrum supports the structure of the enaminecompound, Compound No. 61. FIG. 11 is the ¹H-NMR spectrum of the productin this Production Example 2, and FIG. 12 is an enlarged view of thespectrum of FIG. 11 in the range of from 6 ppm to 9 ppm. FIG. 13 is the¹³C-NMR spectrum in ordinary measurement of the product in ProductionExample 2, and FIG. 14 is an enlarged view of the spectrum of FIG. 13 inthe range of from 110 ppm to 160 ppm. FIG. 15 is the ¹³C-NMR spectrum inDEPT135 measurement of the product in Production Example 2, and FIG. 16is an enlarged view of the spectrum of FIG. 15 in the range of from 110ppm to 160 ppm. In FIG. 11 to FIG. 16, the horizontal axis indicates thechemical shift δ (ppm) of the compound analyzed. In FIG. 11 and FIG. 12,the data written between the signals and the horizontal axis arerelative integral values of the signals based on the integral value, 3,of the signal indicated by the reference numeral 501.

The data of LC-MS and the NMR spectrometry confirm that the compoundobtained herein is the enamine compound, Compound No. 61 (yield: 92%).In addition, the data of LC-MS further confirm that the purity of theenamine compound, Compound No. 61 obtained herein is 99.0%.

As in the above, the three-stage reaction process that comprisesdehydrating condensation, Vilsmeier reaction and Wittig-Horner reactiongives the enamine compound, Compound No. 61 shown in Table 9, and theoverall three-stage yield of the product was 73.5%.

Production Example 3 Production of Compound No. 46

2.0 g (1.0 equivalent) of the enamine-aldehyde intermediate representedby formula (11) obtained in Production Example 1-2, and 1.53 g (1.2equivalents) of a Wittig reagent of the following structural formula(13) were dissolved in 15 ml of anhydrous DMF, and 0.71 g (1.25equivalents) of potassium t-butoxide was gradually added to the solutionat room temperature, then heated up to 50° C., and stirred for 5 hourswhile kept heated at 50° C. The reaction mixture was left cooled, andpoured into excess methanol. The deposit was collected, and dissolved intoluene to prepare a toluene solution thereof. The toluene solution wastransferred into a separating funnel and washed with water, and theorganic layer was taken out. Thus taken out, the organic layer was driedwith magnesium sulfate. Solid matter was removed from the thus-driedorganic layer, which was then concentrated and subjected to silica gelcolumn chromatography to obtain 2.37 g of an yellow crystal.

Thus obtained, the crystal was analyzed through LC-MS, which gave a peakat 566.4 corresponding to the molecular ion [M+H]⁺ of the intendedenamine compound, Compound No. 46 in Table 7 (calculated molecularweight: 565.28) with a proton added thereto. This confirms that thecrystal obtained herein is the enamine compound, Compound No. 46 (yield:92%). In addition, the data of LC-MS further confirm that the purity ofthe enamine compound, Compound No. 46 is 99.8%.

As in the above, the Wittig-Horner reaction of the enamine-aldehydeintermediate represented by formula (11) and the Wittig reagentrepresented by formula (13) gives the enamine compound, Compound No. 46shown in Table 7.

Comparative Production Example 1

Production of Compound of Structural Formula (14)

2.0 g (1.0 equivalent) of the enamine-aldehyde intermediate representedby formula (11) obtained in Production Example 1-2 was dissolved in 15ml of anhydrous THF, and 5.23 ml (1.15 equivalents) of a THF solution ofa Grignard reagent, allylmagnesium bromide prepared from allyl bromideand metal magnesium (molar concentration: 1.0 mol/liter) was graduallyadded to the solution at 0° C. This was stirred at 0° C. for 0.5 hour,and then checked for the reaction progress through thin-layerchromatography, in which no definite reaction product was confirmed butsome different products were found. This was post-processed, extractedand concentrated in an ordinary manner. Then, the reaction mixture wasisolated and purified through silica gel column chromatography.

However, the intended compound of the following structural formula (14)could not be obtained.

Example Example 1

9 parts by weight of dendritic titanium oxide applied with a surfacetreatment with aluminum oxide (chemical formula: Al₂O₃) and zirconiumdioxide (chemical formula: ZrO₂) (manufactured by Ishihara Sangyo Co.:TTO-D-1), and 9 parts by weight of copolymerized nylon resin(manufactured by Toray Co.: Amilan CM8000) were added to a mixed solventof 41 parts by weight of 1,3-dioxolane and 41 parts by weight ofmethanol, and they were dispersed for 12 hours by a paint shaker toprepare a coating solution for intermediate layer. An aluminum substrateof 0.2 mm thickness as a conductive substrate 11 was coated with thecoating solution for intermediate layer by a baker applicator, it wasthen dried to form an intermediate layer 18 of 1 μm film thickness.

After adding 2 parts by weight of an azo compound represented by thefollowing structural formula (15) as a charge generating substance 12into a resin solution obtained by dissolving 1 part by weight ofpolyvinyl butyral resin (manufactured by Sekisui Chemical Industry Co.S-LEC BX-1) into 97 parts by weight of THF, they were dispersed by apaint shaker for 10 hours to prepare a coating solution for chargegenerating layer. The previously formed intermediate layer 18 was coatedwith the obtained coating solution for charge generating layer by abaker applicator, it was then dried to form a charge generating layer 15of 0.3 μm film thickness.

Then, 10 parts by weight of an enamine compound of Exemplified CompoundNo. 1 shown in Table 1 as a charge transporting substance 13, 14 partsby weight of polycarbonate resin (manufactured by Mitsubishi GasChemical Co., Inc.: Z200) as a binder resin 17, and 1 part by weight(about 4% based on the photosensitive layer) of a hindered phenolcompound of Exemplified Compound HP-1 shown in Table 33 as anantioxidant were dissolved in 80 parts by weight of THF, to prepare acoating solution for charge transporting layer. Then, after coating thepreviously formed charge generating layer 15 with the obtained coatingsolution for charge transporting layer by a baker applicator, it wasdried to form a charge transporting layer 16 of 18 μm thickness.

As described above, a layered type electrophotographic photoreceptorhaving a layer structure as shown in FIG. 2 satisfying the constituentfactors of the invention were formed.

Examples 2 to 6

Five kinds of electrophotographic photoreceptors satisfying theconstituent factors of the invention were formed in the same manner asin Example 1 except for using Exemplified Compound No. 3 shown in Table1, Exemplified Compound No. 61 shown in Table 9, Exemplified CompoundNo. 106 shown in Table 16, Exemplified Compound No. 146 shown in Table21 or Exemplified Compound No. 177 shown in Table 26 instead ofExemplified Compound No. 1 as the charge transporting substance 13 inExample 1.

Comparative Example 1

An electrophotographic photoreceptor not satisfying the constituentfactors of the invention was formed in the same manner as in Example 1except for using Comparative Compound A represented by the followingstructural formula (16) instead of Exemplified Compound No. 1 as thecharge transporting substance 13.

Comparative Example 2

An electrophotographic photoreceptor not satisfying the constituentfactors of the invention was formed in the same manner as in Example 1except for using Comparative Compound B represented by the followingstructural formula (17) instead of Exemplified Compound No. 1 as thecharge transporting substance 13 in Example 1.

Comparative Example 3

An electrophotographic photoreceptor not satisfying the constituentfactors of the invention was formed in the same manner as in Example 1except for using Comparative Compound C represented by the followingstructural formula (18) instead of Exemplified Compound No. 1 as thecharge transporting substance 13 in Example 1.

Example 7

In the same manner as in Example 1, an intermediate layer 18 of 1 μmthickness was formed on an aluminum substrate of 0.2 mm thickness as aconductive substrate 11.

Then, 1 part by weight of an azo compound represented by the structuralformula (15) as the charge generating substance 12, 12 parts by weightof polycarbonate resin (manufactured by Mitsubishi Gas Chemical Co.,Inc.: Z-400) as a binder resin 17, 10 parts by weight of an enaminecompound of Exemplified Compound No. 1 shown in Table 1 as the chargetransporting substance 13, 0.5 part by weight (about 2% by weight basedon the photosensitive layer) of a hindered phenol compound ofExemplified Compound HP-1 shown in Table 33 as an antioxidant, 5 partsby weight of 3,5-dimethyl-3′,5′-di-t-butyl diphenoquinone, and 65 partsby weight of THF were dispersed in a ball mill for 12 hours to form acoating solution for photosensitive layer. The previously formedintermediate layer 18 was coated with the obtained coating solution forphotosensitive layer by a baker applicator, it was then dried by hotblow at 110° C. for one hour to form a photosensitive layer 140 of 20 μmthickness.

As described above, a single layer type electrophotographicphotoreceptor having a layer structure shown in FIG. 3 satisfyingconstituent factors of the invention was formed.

Example 8

An electrophotographic photoreceptor satisfying the constituent factorsof the invention was formed in the same manner as in Example 1 exceptfor using X-type non-metal phthalocyanine instead of an azo compoundrepresented by the structure formula (15) as the charge generatingsubstance 12 in Example 1.

Example 9 to 13

An electrophotographic photoreceptor satisfying the constituent factorsof the invention was formed in the same manner as in Example 1 exceptfor using X-type non-metal phthalocyanine instead of the azo compoundrepresented by the structure formula (15) as the charge generatingsubstance 12, and using Exemplified Compound No. 3 shown in Table 1,Exemplified Compound No. 61 shown in Table 9, Exemplified Compound No.106 shown in Table 16, Exemplified Compound No. 146 shown in Table 21,or Exemplified Compound No. 177 shown in Table 26 instead of theExemplified Compound No. 1 as the charge transporting substance 13 inExample 1.

Comparative Examples 4 to 6

Three kinds of electrophotographic photoreceptors not satisfying theconstituent factors of the invention were formed in the same manner asin Example 1 except for using X-type non-metal phthalocyanine instead ofthe azo compound represented by the structural formula (15) as thecharge generating substance 12, and using Comparative Compound Arepresented by the structural formula (16), Comparative Compound Brepresented by the structural formula (17) or Comparative Compound Crepresented by the structural formula (18) instead of ExemplifiedCompound No. 1 as the charge transporting substance 13 in Example 1.

Comparative Example 7

An electrophotographic photoreceptor not satisfying the constituentfactors of the invention was formed in the same manner as in Example 1except for using X-type non-metal phthalocyanine instead of the azocompound represented by the structural formula (15) as the chargegenerating substance 12, and using Comparative Compound D represented bythe structural formula (19) instead of Exemplified Compound No. 1 as thecharge transporting substance 13 in Example 1.

Comparative Example 8

An electrophotographic photoreceptor not satisfying the constituentfactors of the invention was formed in the same manner as in Example 1except for using X-type non-metal phthalocyanine instead of the azocompound represented by the structural formula (15) as the chargegenerating substance 12, and using Comparative Compound E represented bythe structural formula (20) instead of Exemplified Compound No. 1 as thecharge transporting substance 13 in Example 1.

<Evaluation 1>

For each of the electrophotographic photoreceptors manufactured inExamples 1 to 13 and Comparative Examples 1 to 8, initialcharacteristics and characteristics after repetitive use were evaluatedby using an electrostatic copy paper testing apparatus (manufactured byKawaguchi Denki Seisakusho Co.: EPA-8200). The evaluation was conductedin such a manner as described below under an N/N (NormalTemperature/Normal Humidity) circumstance at a temperature of 22° C. andat a relative humidity of 65% (22° C./65% RH), and under an L/L (Lowtemperature/Low Humidity) circumstance at a temperature of 5° C. and ata relative humidity of 20% (5° C./20% RH).

The surface of the photoreceptor was charged by applying a voltage atnegative (−)5 kV to a photoreceptor and the surface potential on thephotoreceptor in this case was measured as a charge potential V₀ (V).However, in a case of the single layered type photoreceptor in Example7, the surface of the photoreceptor was charged by applying a voltage atpositive (+) 5 kV.

Then, exposure was applied to the charged surface of the photoreceptor,and the energy required for decaying the surface potential on thephotoreceptor to one-half of the charge potential V₀ was measured as ahalf-decay exposure amount E_(1/2) (μJ/cm²). Further, the surfacepotential on the photoreceptor at the time with lapse of 10 sec from thestart of exposure was measured as a residual potential Vr (V). For theexposure, a white light at an exposure energy of 1 μW/cm² was used inthe case of Examples 1 to 7 and Comparative Examples 1 to 3 using theazo compound represented by the structural formula (15) as the chargegenerating substance 12, and a light at a wavelength of 780 nm and at anexposure energy of 1 μm/cm² obtained by spectralyzing by a monochrometerwas used in the case of Examples 8 to 13 and Comparative Examples 4 to 8using X-type non-metal phthalocyanine as the charge generating substance12. The results of the measurements were used as the results ofmeasurements in the initial state.

After repeating the operation of charging and exposure for 5000 times asone cycle, the charge potential V₀, the half-decay exposure amountE_(1/2), and the residual potential V_(r) were measured in the samemanner as in the evaluation for initial characteristics. The results ofthe measurements were used as the results of measurements afterrepetitive use.

Table 56 shows the results of the measurements for the initialcharacteristics and the characteristics after repetitive use.

TABLE 56 N/N: 22° C./65% RH Initial state Charge transporting E_(1/2)Charge generating substance substance (μJ/cm²) V₀(V) Vr(V) Example 1 AzoCompound (15) Exemplified Compound 1 0.16 −584 −10 Example 2 AzoCompound (15) Exemplified Compound 3 0.15 −586 −13 Example 3 AzoCompound (15) Exemplified Compound 61 0.14 −583 −14 Example 4 AzoCompound (15) Exemplified Compound 106 0.14 −586 −13 Example 5 AzoCompound (15) Exemplified Compound 146 0.15 −581 −15 Example 6 AzoCompound (15) Exemplified Compound 177 0.16 −585 −15 Comp. Example 1 AzoCompound (15) Comparative Compound A 0.20 −578 −35 Comp. Example 2 AzoCompound (15) Comparative Compound B 0.21 −575 −38 Comp. Example 3 AzoCompound (15) Comparative Compound C 0.21 −591 −42 Example. 7 AzoCompound (15) Exemplified Compound 1 0.24 559 19 Example. 8 X-typenon-metal phthalocyanine Exemplified Compound 1 0.11 −585 −10 Example. 9X-type non-metal phthalocyanine Exemplified Compound 3 0.12 −581 −12Example. 10 X-type non-metal phthalocyanine Exemplified Compound 61 0.10−584 −9 Example 11 X-type non-metal phthalocyanine Exemplified Compound106 0.10 −586 −9 Example 12 X-type non-metal phthalocyanine ExemplifiedCompound 146 0.13 −583 −11 Example 13 X-type non-metal phthalocyanineExemplified Compound 177 0.13 −581 −13 Comp. Example 4 X-type non-metalphthalocyanine Comparative Compound A 0.15 −586 −25 Comp. Example 5X-type non-metal phthalocyanine Comparative Compound B 0.15 −585 −28Comp. Example 6 X-type non-metal phthalocyanine Comparative Compound C0.15 −581 −30 Comp. Example 7 X-type non-metal phthalocyanineComparative Compound D 0.13 −585 −98 Comp. Example 8 X-type non-metalphthalocyanine Comparative Compound E 0.15 −587 −22 N/N: 22° C./65% RHL/L: 5° C./20% RH After repetitive use Initial state After repetitiveuse E_(1/2) E_(1/2) E_(1/2) (μJ/cm²) V₀(V) Vr(V) (μJ/cm²) V₀(V) Vr(V)(μJ/cm²) V₀(V) Vr(V) Example 1 0.18 −574 −15 0.18 −586 −15 0.19 −576 −18Example 2 0.16 −576 −17 0.16 −587 −13 0.18 −579 −19 Example 3 0.15 −578−18 0.16 −585 −18 0.18 −573 −20 Example 4 0.16 −577 −15 0.16 −584 −160.17 −576 −19 Example 5 0.16 −575 −19 0.17 −581 −16 0.20 −575 −19Example 6 0.19 −573 −18 0.18 −583 −18 0.22 −572 −23 Comp. Example 1 0.22−576 −36 0.42 −579 −50 0.45 −571 −51 Comp. Example 2 0.24 −577 −42 0.44−578 −55 0.48 −577 −59 Comp. Example 3 0.25 −589 −54 0.45 −581 −55 0.51−579 −65 Example. 7 0.26 542 25 0.26 551 25 0.29 540 30 Example. 8 0.12−573 −13 0.13 −583 −12 0.15 −573 −15 Example. 9 0.12 −574 −15 0.15 −584−15 0.18 −576 −18 Example. 10 0.11 −573 −13 0.12 −587 −12 0.14 −575 −15Example 11 0.12 −574 −12 0.11 −586 −10 0.13 −572 −13 Example 12 0.15−574 −15 0.16 −586 −13 0.18 −574 −16 Example 13 0.14 −575 −18 0.17 −584−14 0.19 −573 −18 Comp. Example 4 0.17 −576 −27 0.36 −580 −45 0.38 −578−46 Comp. Example 5 0.19 −575 −35 0.38 −582 −48 0.42 −575 −55 Comp.Example 6 0.19 −575 −40 0.38 −579 −50 0.45 −570 −59 Comp. Example 7 0.18−571 −115 0.21 −580 −115 0.23 −572 −123 Comp. Example 8 0.18 −574 −310.35 −582 −49 0.44 −572 −60

It was found from the Table 56 that all of the photoreceptors inExamples 1 to 13 and Comparative Examples 1 to 8 each containing theantioxidant in the photosensitive layer had less fatigue degradationupon repetitive use showing less difference between the result ofmeasurement in the initial state and the result of measurement afterrepetitive use.

Further, it was found that among photoreceptors of Examples 1 to 13 andComparative Examples 1 to 8, the photoreceptors of Examples 1 to 13using the enamine compound represented by the general formula (1) forthe charge transporting substance 13 had higher sensitivity showing lesshalf-decay exposure amount E_(1/2) and were more excellent in the lightresponsivity showing smaller absolute value for residual potential Vr ascompared with the photoreceptors of Comparative Examples 1 to 8 usingComparative Compounds A, B, C, D or E for the charge transportingsubstance 13. Further, it was found that the photoreceptors of Examples1 to 13 was more excellent in the stability of characteristics relativeto the change of circumstances showing less difference between theresult of measurement under N/N circumstance and the result ofmeasurement under an L/L circumstance, and caused no deterioration forthe characteristics even under the L/L circumstance, whereas thephotoreceptors of Comparative Examples 1 to 8 show more differencebetween the result of measurement under the N/N circumstance and theresult of measurement under the L/L circumstance, and showed largerdeterioration for the characteristics under the L/L circumstance.

Example 14

21 parts by weight of titanium oxide (manufactured by Ishihara SangyoCo.: TTO55A) and 39 parts by weight of copolymerized nylon resin(manufactured by Toray Co.: Amilan CM8000) were added to a mixed solventof 329 parts by weight of methanol and 611 parts by weight of1,2-dichloroethane, and they were dispersed using a paint shaker for 8hours to prepare a coating solution for intermediate layer. An aluminumsubstrate of 0.2 mm thickness, as a conductive substrate 11 was coatedwith the obtained coating solution for intermediate layer by a bakerapplicator, it was then dried to form an intermediate layer 18 of 1 μmthickness.

Then, after adding 2 parts by weight of Y-type oxotitaniumphthalocyanine as a charge generating substance 12 to a resin solutionobtained by dissolving 1 part by weight of polyvinyl butyral resin(manufactured by Sekisui Chemical Industry Co.: S-LEC BX-1) in 97 partsby weight of methyl ethyl ketone, they were dispersed by a paint shakerfor 10 hours to prepare a coating solution for charge generating layer.The previously formed intermediate layer 18 was coated with the obtainedcoating solution for charge generating layer, it was then dried to forma charge generating layer 15 of 0.4 μm thickness.

Then, 10 parts by weight of the enamine compound of Exemplified CompoundNo. 61 shown in Table 9 as a charge transporting substance 13, 18 partby weight of polycarbonate resin (manufactured by Mitsubishi GasChemical Co., Inc.: PCZ400) as a binder resin 17, and 1.4 parts byweight (about 5% based on the photosensitive layer) of a hindered phenolcompound of Exemplified Compound HP-1 shown in Table 33 as anantioxidant were dissolved in 100 parts by weight of THF, to prepare acoating solution for charge transporting layer. The previously formedcharge generating layer 15 was coated with the obtained coating solutionfor charge transporting layer by a baker applicator, it was then driedto form a charge transporting layer 16 of 23 μm film thickness.

As described above, a stacked type electrophotographic photoreceptorhaving a layer structure shown in FIG. 2 satisfying the constituentfactors of the invention was formed.

Examples 15 to 17

Three kinds of electrophotographic photoreceptors satisfying theconstituent factors of the invention were formed in the same manner asin Example 14 except for using Exemplified Compound HP-9 shown in Table33, Exemplified Compound P-7 shown in Table 40, or Exemplified CompoundS-6 shown in Table 45 instead of the Exemplified Compound HP-1 as anantioxidant in Example 14.

Examples 18 to 20

Three kinds of electrophotographic photoreceptors satisfying theconstituent factors of the invention were formed in the same manner asin Example 14 except for using Exemplified Compound HA-3 shown in Table47, Exemplified Compound HA-10 shown in Table 48, or ExemplifiedCompound TZ-5 shown in Table 50 as a light stabilizer instead ofExemplified Compound HP-1 as an antioxidant in Example 14.

Example 21

An electrophotographic photoreceptor satisfying the constituent factorsof the invention was formed in the same manner as in Example 14 exceptfor using Exemplified Compound No. 3 shown in Table 1 instead ofExemplified Compound No. 61 as a charge transporting substance 13, andusing Exemplified Compound HP-26 shown in Table 35 instead ofExemplified Compound HP-1 as antioxidant in Example 14.

Example 22

An electrophotographic photoreceptor satisfying the constituent factorsof the invention was formed in the same manner as in Example 14 exceptfor using Exemplified Compound No. 146 shown in Table 21 instead ofExemplified Compound No. 61 as a charge transporting substance 13, andusing Exemplified Compound HA-10 shown in Table 48 as a light stabilizerinstead of Exemplified compound HP-1 as an antioxidant in Example 14.

Example 23

After storing the coating solution for charge transporting layerobtained in Example 14 under a circumstance at a temperature of 40° C.in a dark place for one month, an electrophotographic photoreceptorsatisfying the constituent factors of the invention was formed in thesame manner as in Example 14 using the coating solution for chargetransporting layer.

Example 24

An electrophotographic photoreceptor satisfying the constituent factorsof the invention was formed in the same manner as in Example 14 exceptfor changing the amount of the hindered phenol compound of ExemplifiedCompound HP-1 as an antioxidant to 5.4 parts (about 16% by weight basedon the photosensitive layer) in Example 14.

Example 25

An electrophotographic photoreceptor satisfying the constituent factorsof the invention was formed in the same manner as in Example 14 exceptfor using 3.5 parts by weight (about 11% by weight based on thephotosensitive layer) of the hindered amine compound of ExemplifiedCompound HA-3 shown in Table 47 as a light stabilizer instead of 1.4parts by weight of the hindered phenol compound of Exemplified CompoundHP-1 as an antioxidant in Example 14.

Comparative Example 9

An electrophotographic photoreceptor not satisfying the constituentfactors of the invention was formed in the same manner as in Example 14except for not using the hindered phenol compound of ExemplifiedCompound HP-1 as an antioxidant in Example 14.

Comparative Example 2

After storing the coating solution for charge transporting layerobtained in Comparative Example 1 under a circumstance at a temperatureof 40° C. in a dark place for one month, an electrophotographicphotoreceptor not satisfying the constituent factors of the inventionwas formed using the coating solution for charge transporting layer inthe same manner as in Example 14.

<Evaluation 2>

For each of the electrophotographic photoreceptors manufactured inExamples 14 to 25 and Comparative Examples 9 and 10, initialcharacteristics and characteristics after repetitive use were evaluatedby a so-called Dynamic method for conducting charge and measurementalternately while rotating a rotational disk on which a sample wasplaced using an electrostatic copy paper testing apparatus (manufacturedby Kawaguchi Denki Seisakusho Co.: EPA-8200). The evaluation wasconducted as described below under a high temperature and high humiditycircumstance at a temperature of 35° C. and relative humidity of 85%(35° C./85% RH).

The surface of the photoreceptor was charged by applying a voltage atnegative (−)600V to a photoreceptor while rotating a rotatable disk onwhich a sample was placed at a number of revolution of 1100 rpm/min.Then, exposure was applied to the charged surface of the photoreceptorby a monochromatic light having a wavelength of 780 nm at an exposureenergy of 1 μW/cm², and the energy required for decaying the surfacepotential on the photoreceptor to one-half from negative (−)600V as thecharge potential to negative (−)300V, was measured as a half-decayexposure amount E_(1/2) (μJ/cm²). Further, exposure was applied to thesurface of the photoreceptor charged to negative (−)600V at an exposureamount of 2 μJ/cm², and the surface potential on the photoreceptor justafter the exposure was measured as the residual potential V_(R) (V). Theresults of the measurements were used as the results at initial state.

Then, after repeating the operation of the charging and exposure for50000 times as one cycle, the half-decay exposure amount E_(1/2) and theresidual potential V_(R) were measured in the same manner for those inthe initial state. The results of the measurements were used as theresults of measurement after repetitive use.

Table 57 shows the results of measurements in the initial state andafter repetitive use.

TABLE 57 Antioxidant · light stabilizer After Charge transportingExemplified Content Initial stage repetitive use substance Compound (wt%) E_(1/2)(μJ/cm2) V_(n)(V) E_(1/2)(μJ/cm2) V_(n)(V) Remarks Example 14Exemplified Compound 61 HP-1 5 0.15 −15 0.17 −21 Example 15 ExemplifiedCompound 61 HP-9 5 0.15 −18 0.18 −25 Example 16 Exemplified Compound 61P-7 5 0.15 −22 0.18 −30 Example 17 Exemplified Compound 61 S-6 5 0.16−28 0.2 −35 Example 18 Exemplified Compound 61 HA-3 5 0.14 −15 0.17 −22Example 19 Exemplified Compound 61 HA-10 5 0.15 −19 0.17 −25 Example 20Exemplified Compound 61 TZ-5 5 0.15 −22 0.18 −30 Example 21 ExemplifiedCompound 3 HP-26 5 0.17 −25 0.21 −31 Example 22 Exemplified Compound 146HA-10 5 0.13 −18 0.17 −23 Example 23 Exemplified Compound 61 HP-1 5 0.16−16 0.18 −23 Manufactured after storing coating solution for one monthExample 24 Exemplified Compound 61 HP-1 16 0.16 −52 0.18 −58 Example 25Exemplified Compound 61 HA-3 11 0.16 −65 0.18 −69 Comp. Example 9Exemplified Compound 61 None 0.15 −15 0.22 −55 Comp. Example 10Exemplified Compound 61 None 0.18 −75 0.25 −120 Manufactured afterstoring coating solution for one month

It was found from Table 57 that among the photoreceptors of Examples 14to 25 and Comparative Examples 9 and 10 using the enamine compoundrepresented by the general formula (1) for the charge transportingsubstance 13, the photoreceptors of Examples 14 to 25 containing anantioxidant or a light stabilizer in the photosensitive layer showedless fatigue degradation upon repetitive use, showing smaller differencebetween the result of the measurements in the initial state and theresult of the measurements after repetitive use. On the contrary, it wasfound that the photoreceptors of Comparative Examples 9 and 10containing none of the antioxidant or light stabilizer in thephotosensitive layer showed a larger difference between the result ofmeasurements in the initial state and the result of measurements afterrepetitive use and caused larger fatigue degradation upon repetitiveuse.

Further, it was found from the comparison between Example 14 and Example23 that in a case where the antioxidant was added to the coatingsolution for charge transporting layer, photoreceptors havingsubstantially identical characteristics were obtained even whenphotoreceptors were formed immediately after the preparation of thecoating solution for charge transporting layer or when they were formedafter lapse of a long time. On the contrary, in a case where the coatingsolution for charge transporting layer was incorporated with none of theantioxidant or light stabilizer as in the case of Comparative Example 9and Comparative Example 10, the characteristics of the photoreceptor ofComparative Examples 9 prepared immediately after preparation of thecoating liquid for charge transporting layer greatly differ from thecharacteristics of the photoreceptor of Comparative Example 10 preparedafter lapse of a long time. In particular, the photoreceptor ofComparative Example 10 showed a larger absolute value of the residualpotential V_(R) as compared with that of the photoreceptor ofComparative Example 9 and caused degradation of the light responsivity.Based on the results described above, it can be seen that the stabilityof the coating liquid was improved by addition of the antioxidant.

Further, it was found from the comparison between Example 14 and Example24 that, the photoreceptor of Example 24 having the content of theantioxidant in the photosensitive layer of exceeding 15% by weight washad somewhat larger absolute value of the residual potential V_(R) andwas somewhat poor in the light responsivity compared with thephotoreceptor of Example 14 with the content of the antioxidant in thephotosensitive layer within a range of from 0.1 to 15% by weight.

Further, it was found from the comparison between Example 18 and Example25 that the photoreceptor of Example 25 having the content of the lightstabilizer in the photosensitive layer of exceeding 10% by weight showedsomewhat larger absolute value of the residual potential V_(R) and wassomewhat poor in the light responsivity compared with that of thephotoreceptor of Example 18 having the content of the light stabilizerin the photosensitive layer within a range of from 0.1 to 10% by weight.

Example 26

21 parts by weight of titanium oxide (manufactured by Ishihara SangyoCo.: TTO55A) and 39 parts by weight of copolymerized nylon resin(manufactured by Toray Co.: Amilan CM8000) were added to a mixed solventof 329 parts by weight of methanol and 611 parts by weight of1,2-dichloroethane, and they were dispersed for 8 hours using a paintshaker to prepare a coating solution for intermediate layer. Theobtained coating solution for intermediate layer was filled in a coatingtank. A cylindrical aluminum conductive substrate 11 of 40 mm diameterand 340 mm length was dipped in the coating tank and then pulled up anddried to form an intermediate layer 18 of 1.0 μm thickness on the outerperipheral surface of the conductive substrate 11.

Then, 2 parts by weight of oxotitanium phthalocyanine having a crystalstructure showing an apparent diffraction peak at least at a Bragg angleof 2θ (error: 2θ±0.2°) of 27.2° in the X-ray diffraction spectrum forCu-Kαcharacteristic X-rays (wavelength: 1.54 Å) as the charge generatingsubstance 12, 1 part by weight of polyvinyl butyral resin (manufacturedby Sekisui Chemical Industry Co.: S-LEC BX-S) and 97 parts by weight ofmethyl ethyl ketone were mixed and dispersed by a paint shaker toprepare a coating solution for charge generating layer. The outercircumferential surface of the previously formed intermediate layer 18was coated with the obtained coating solution for charge generatinglayer by a dip coating method, which was the same method for theintermediate layer 18, and it was then dried to form a charge generatinglayer 15 of 0.4 μm thickness.

Then, 10 parts by weight of Exemplified Enamine Compound No. 61 as thecharge transporting substance 13, 18 parts by weight of polycarbonateresin (manufactured by Mitsubishi Engineering Plastics Co.: EupironZ200) as the binder resin 17, 1.4 parts by weight (about 5% by weightbased on the photosensitive layer) of the hindered phenol compound ofExemplified Compound HP-1 shown in Table 33 as the antioxidant, and0.004 part by weight of dimethylpolysiloxane (Shin-Etsu Chemical Co.,Ltd.: KF-96) were dissolved in 110 parts by weight of tetrahydrofuran toprepare a coating solution for charge transporting layer. The outercircumferential surface of the previously formed charge generating layer15 was coated with the obtained coating solution of charge transportinglayer by a dip coating method, which was the same method for theintermediate layer 18, and it was then dried at 110° C. for one hour toform a charge transporting layer 16 of 23 μm thickness.

As described above, the electrophotographic photoreceptor having aconstitution shown in FIG. 2 satisfying the constituent factors of theinvention was formed.

Examples 27 and 28

Two kinds of electrophotographic photoreceptors satisfying theconstituent factors of the invention were formed in the same manner asin Example 26 except for using Exemplified Compound P-36 shown in Table42 or Exemplified Compound S-12 shown in Table 46 instead of ExemplifiedCompound HP-1 as an antioxidant in Example 26.

Examples 29 and 30

Two kinds of electrophotographic photoreceptors satisfying theconstituent factors of the invention were formed in the same manner asin Example 26 except for using Exemplified Compound HA-3 shown in Table47 or Exemplified Compound TZ-4 shown in Table 50 as a light stabilizerinstead of Exemplified Compound HP-1 as an antioxidant in Example 26.

Example 31

An electrophotographic photoreceptor satisfying the constituent factorsof the invention was formed in the same manner as in Example 26 exceptfor using Exemplified Compound X-19 shown in Table 55 instead ofExemplified Compound HP-1 as an antioxidant in Example 26.

Example 32

An electrophotographic photoreceptor satisfying the constituent factorsof the invention was formed in the same manner as in Example 26 exceptfor using Exemplified Compound 159 shown in Table 23 instead ofExemplified Compound No. 61 as the charge transporting substance inExample 26.

Example 33

An electrophotographic photoreceptor satisfying the constituent factorsof the invention was formed in the same manner as in Example 26 exceptfor using 1 part by weight of the hindered phenol compound ofExemplified Compound HP-1 and 0.4 part of the hindered amine compound ofExemplified Compound HA-3 shown in Table 47 as a light stabilizer to beused as a mixture (in an amount of about 5% by weight in total based onthe photosensitive layer) instead of 1.4 parts by weight of the hinderedphenol compound of Exemplified Compound HP-1 as an antioxidant inExample 26.

Example 34

An electrophotographic photoreceptor satisfying the constituent factorsof the invention was formed in the same manner as in Example 26 exceptfor using 0.3 part by weight of the hindered phenol compound ofExemplified Compound HP-26 shown in Table 35 as an antioxidant and 0.2part of the hindered amine compound of Exemplified Compound HA-10 shownin Table 48 as a light stabilizer to be used as a mixture (in an amountof about 2% by weight of content in total based on the photosensitivelayer) instead of 1.4 parts by weight of the hindered phenol compound ofExemplified Compound HP-1 as an antioxidant in example 26.

Example 35

An electrophotographic photoreceptor satisfying the constituent factorsof the invention was formed in the same manner as in Example 26 exceptfor using 1 part by weight of the hindered phenol compound ofExemplified Compound HP-1 and 1 part of Exemplified Compound X-16 shownin Table 54 as a mixture (about 7% by weight of content in total basedon the photosensitive layer) instead of 1.4 parts by weight of thehindered phenol compound of Exemplified Compound HP-1 as an antioxidantin Example 26.

Comparative Example 11

An electrophotographic photoreceptor not satisfying the constituentfactors of the invention was formed in the same manner as in Example 26except for using the hindered phenol compound of Exemplified CompoundHP-1 as an antioxidant in Example 26.

<Evaluation 3>

Each of the electrophotographic photoreceptors formed in Examples 26 to35 and Comparative Example 11 described above were loaded on acommercially available small-sized digital copier (manufactured by SharpCorp.: AR-C260) modified such that the surface potential of thephotoreceptors in the image forming process could be measured with asurface potential meter (manufactured by GEN-TECH Inc.: CATE751). Thesurface potential of the photoreceptor was measured just after chargingas a charge potential V₀ (V) under a circumstance at a temperature of22° C. and a relative humidity of 20% (22° C./20% RH) Further thesurface potential of the photoreceptor was measured just after theexposure of a laser light as an after exposure potential V_(L) (V). Theresults of the measurement were used as the results of measurement in aninitial state.

Then, after conducting actual reproduction aging of copying test imagesof a predetermined pattern on 10,000 common paper, the charge potentialV₀ (V) and the after exposure potential V_(L) (V) were measured in thesame manner as in the initial state. The results of the measurement wereused as results of the measurement after actual reproduction aging.

Then, half-tone images were formed on JIS (Japan Industrial Standards)A3 common paper. In this case, the half tone images are images in whichshading of image was expressed by black and white gradation dots. Theobtained images were visually observed, and the image quality wasevaluated with respect to the extent of image defects such as blanking,black streaks and image blurring.

The image quality was evaluated with reference to the following scores.

-   A: Good. No image defects.-   B: Somewhat poor. Somewhat negligible image defects.-   C: Poor. Distinct image defects.

Table 58 shows the results of measurements in the initial state andthose after actual reproduction aging and the result of evaluation forthe images after actual reproduction aging.

TABLE 58 After actual copying Evaluation Charge transporting Initialstage and aging of image substance Antioxidant · light stabilizer V₀(V)V_(L) (V) V₀(V) V_(L)(V) quality Example 26 Exemplified Compound 61 HP-1−605 −45 −602 −55 A Example 27 Exemplified Compound 61 P-36 −604 −48−605 −59 B Example 28 Exemplified Compound 61 S-12 −600 −51 −603 −65 BExample 29 Exemplified Compound 61 HA-3 −608 −46 −605 −54 A Example 30Exemplified Compound 61 TZ-4 −604 −49 −608 −61 B Example 31 ExemplifiedCompound 61 X-19 −602 −49 −600 −61 B Example 32 Exemplified Compound 159HP-1 −608 −45 −605 −54 A Example 33 Exemplified Compound 61 HP-1 + HA-3−607 −45 −601 −52 A Example 34 Exemplified Compound 61 HP-26 + HA-10−608 −46 −605 −53 A Example 35 Exemplified Compound 61 HP-1 + X-16 −604−46 −604 −52 A Comp. Example 11 Exemplified Compound 61 None −602 −48−485 −115 C

From Table 58, it has been found that among the photoreceptors ofExamples 26 to 35 and Comparative Example 11 using the enamine compoundrepresented by the general formula (1) for the charge transportingsubstance 13, the photoreceptors of Examples 26 to 35 containing theantioxidant and the light stabilizer in the photosensitive layer showedno remarkable lowering of the absolute value for the charged potentialV₀ even after exposure to ozone or Nox during charging, exposure, andactual reproduction aging under load such as exposure to light or heatupon charge elimination and no remarkable increase of the absolute valuefor the after exposure potential V_(L) and had excellent electricalcharacteristics. Further, images formed by a copying machine mountingphotoreceptors of Examples 26 to 35 after actual reproduction agingscarcely showed image defects such as image blurring due to the fatiguedeterioration and were at a substantially good quality.

On the contrary, the photoreceptor of Comparative Example 11 containingneither the antioxidant nor the light stabilizer in the photosensitivelayer showed the same extent of charge potential V₀ and the afterexposure potential V_(L) as those of the photoreceptors of Examples 26to 35 in the initial state, but the absolute value for the chargepotential V₀ was greatly lowered after the actual reproduction aging andthe absolute value for the after exposure potential V_(L) was increasedremarkably. Further, apparent image defects were formed in the imagesformed by the copying machine mounting the photoreceptor of ComparativeExample 11 after actual reproduction aging.

As described above, by the incorporation of the enamine compoundrepresented by the general formula (1) and at least one of theantioxidant and the light stabilizer in combination to thephotosensitive layer, it was possible to obtain a highly reliableelectrophotographic photoreceptor having high chargeability, sensitivityand light responsivity, not suffering from deterioration of thecharacteristics described above even when it is used under a lowtemperature circumstance, stable against an active gas such as ozone orNOx, and UV-rays and heat and with less fatigue deterioration afterrepetitive use.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription and all changes which come within the meaning and the rangeof equivalency of the claims are therefore intended to be embracedtherein.

INDUSTRIAL APPLICABILITY

As has been described above, according to the invention, since thephotosensitive layer contains an enamine compound of high chargemovability having a specified structure and at least one of theantioxidant and the light stabilizer in the photosensitive layer, it ispossible to obtain a highly reliable electrophotographic photoreceptorhaving high chargeability, sensitivity and light responsivity, notsuffering from lowering of the characteristics described above even in acase when it is used under a low temperature circumstance or in a highspeed electrophotographic process, stable against an active gas such asozone or NOx, UV-rays and heat, and with less fatigue deteriorationafter repetitive use. Further, the stability of the coating solutionupon forming the photosensitive layer by coating can be increased toimprove the stability of quality and the productivity of theelectrophotographic photoreceptor.

Further, according to the invention, since the photosensitive layercontains an enamine compound of a specified structure having aparticularly high charge movability, and synthesized relatively easilyat a high yield and capable of being produced at a reduced cost, it ispossible to manufacture an electrophotographic photoreceptor havinghigher sensitivity and light responsivity at a reduced manufacturingcost.

Further, according to the invention, since the photosensitive layercontains a specified antioxidant, it is possible to particularlysuppress the decomposition or degradation of the enamine compound havingthe specified structure contained as the charge transporting substancein the photosensitive layer to further mitigate the fatiguedeterioration upon repetitive use and further improve the durability ofthe electrophotographic photoreceptor, as well as further increase thestability of the coating solution upon forming the photosensitive layerby coating to further improve the stability of quality and theproductivity of the electrophotographic photoreceptor.

Further, according to the invention, since the photosensitive layercontains a specified light stabilizer, it is possible to particularlysuppress the decomposition or degradation of the enamine compound havingthe specified structure contained as the charge transporting substancein the photosensitive layer to further mitigate the fatiguedeterioration upon repetitive use and further improve the durability ofthe electrophotographic photoreceptor, as well as further increase thestability of the coating solution upon forming the photosensitive layerby coating to further improve the stability of quality and theproductivity of the electrophotographic photoreceptor.

Further, according to the invention, since the content of theantioxidant contained in the photosensitive layer is selected within apreferred range, this can provide a sufficient effect for theimprovement of the durability of the electrophotographic photoreceptorand improvement for the stability of the coating solution, and loweringof the characteristics of the electrophotographic photoreceptor causedby incorporation of the antioxidant can be minimized.

Further, according to the invention, since the content of the lightstabilizer contained in the photosensitive layer is selected within apreferred range, can provide a sufficient effect for the improvement ofthe durability of the electrophotographic photoreceptor and improvementfor the stability of the coating solution, and lowering of thecharacteristics of the electrophotographic photoreceptor caused byincorporation of the light stabilizer can be minimized.

Further, according to the invention, since the image forming apparatushas a highly reliable electrophotographic photoreceptor having highchargeability, sensitivity and light responsivity, not suffering fromdeterioration of the characteristics described above even in a casewhere it is used under a low temperature circumstance or in a high speedelectrophotographic process or in a case where it is exposed to thelight, stable against an active gas such as ozone or NOx and UV-rays andheat, and with less fatigue deterioration upon repetitive use, it ispossible to obtain a highly reliable image forming apparatus capable ofproviding high quality images stably over a long time under variouscircumstances and with no deterioration of image quality caused by theexposure of the electrophotographic photoreceptor to the light, forexample, during maintenance.

1. An electrophotographic photoreceptor comprising: a conductivesubstrate composed of a conductive material; and a photosensitive layerdisposed on the conductive substrate and containing an enamine compoundrepresented by the following general formula (1), and a hindered phenolcompound having a hindered phenol structural unit as an antioxidant anda light stabilizer selected from the group consisting of HA-3, HA-10 andX-16:

 wherein Ar¹ and Ar² each represent an aryl group which may have asubstituent or a heterocyclic group which may have a substituent; Ar³represents an aryl group which may have a substituent, a heterocyclicgroup which may have a substituent, an aralkyl group which may have asubstituent, or an alkyl group which may have a substituent; Ar⁴ and Ar⁵each represent a hydrogen atom, a aryl group which may have asubstituent, a heterocyclic group which may have a substituent, anaralkyl group which may have a substituent, or an alkyl group which mayhave a substituent, but it is excluded that Ar⁴ and Ar⁵ are hydrogenatoms at the same time; Ar⁴ and Ar⁵ may bond to each other via an atomor an atomic group to form a cyclic structure; “a” represents an alkylgroup which may have a substituent, an alkoxy group which may have asubstituent, an dialkylamino group which may have a substituent, an arylgroup which may have a substituent, a halogen atom, or a hydrogen atom;m indicates an integer of from 1 to 6; when m is 2 or more, then the “a”s may be the same or different and may bond to each other to form acyclic structure; R¹ represents a hydrogen atom, a halogen atom, or analkyl group which may have a substituent; R², R³ and R⁴ each represent ahydrogen atom, an alkyl group which may have a substituent, an arylgroup which may have a substituent, a heterocyclic group which may havea substituent, or an aralkyl group which may have a substituent; nindicates an integer of from 0 to 3; when n is 2 or 3, then the R²s maybe the same or different and the R³s may be the same or different, butwhen n is 0, Ar³ is a heterocyclic group which may have a substituent,said HA-3, HA-10 and X-16 having the following structures:

 respectively.
 2. The electrophotographic photoreceptor of claim 1,wherein the enamine compound represented by the general formula (1) isan enamine compound represented by the following general formula (2):

wherein “b”, “c” and “d” each represent an alkyl group which may have asubstituent, an alkoxy group which may have a substituent, adialkylamino group which may have a substituent, an aryl group which mayhave a substituent, a halogen atom, or a hydrogen atom; “i”, “k” and “j”each indicate an integer of from 1 to 5; when “i” is 2 or more, then the“b”s may be the same or different and may bond to each other to form acyclic structure; when “k” is 2 or more, then the “c”s may be the sameor different and may bond to each other to form a cyclic structure; andwhen “j” is 2 or more, then the “d”s may be the same or different andmay bond to each other to form a cyclic structure; Ar⁴, Ar⁵, “a” and “m”represent the same as those defined in formula (1).
 3. Theelectrophotographic photoreceptor of claim 1, wherein the enaminecompound represented by the general formula (1) is an enamine compoundrepresented by the following general formula (1 a):

wherein Ar¹ and Ar² each represents a phenyl group; Ar³ represents atolyl group, p-methoxyphenyl group, naphthyl group, or5-methyl-2-thienyl group; Ar⁴ represents a hydrogen atom, lower alkylgroup or phenyl group; Ar⁵ represents a phenyl group or p-methoxyphenylgroup; and n represents an integer of 1 to
 2. 4. The electrophotographicphotoreceptor of claim 1, wherein the hindered phenol compound is acompound represented by the following structural formula (I-a):


5. The electrophotographic photoreceptor of any one of claims 1-3 and 4,wherein the photosensitive layer contains 0.1 to 15% by weight of theantioxidant.
 6. The electrophotographic photoreceptor of any one ofclaims 1-3 and 4, wherein the photosensitive layer contains 0.1 to 10%by weight of the light stabilizer.
 7. An image forming apparatuscomprising: the electrophotographic photoreceptor of any one of claims1-3 and 4; charging means for charging the electrophotographicphotoreceptor; exposure means for applying exposure to the chargedelectrophotographic photoreceptor; and developing means for developingelectrostatic latent images formed by exposure.